March 23, 2006 to June 10, 2009 [recurring];

June 11, 2009 to August 27, 2010 [contract]

February 28, 2014 [guest appearance]

March 9, 2018 to April 5, 2018 [guest appearances]

Thomas Forrester is the first-born child of Ridge Forrester and Taylor Hayes. While Taylor was pregnant, Ridge's brother, Thorne Forrester, wanted to claim Taylor's baby as his since Thorne was in love with Taylor, who was on the outs with Ridge. Soon Taylor and Ridge reunited and named their baby after St. Thomas, where Ridge had originally proposed to Taylor.

Baby Thomas was briefly the target of the infamous Sheila Carter, who wanted to keep her nemesis, Stephanie Forrester, away from her husband, psychiatrist James Warwick: Sheila snipped a lock of Thomas' hair and presented it to Stephanie, threatening to kill Thomas if Stephanie didn't heed Sheila's warning.

Thomas and his family were devastated when Taylor was killed in an altercation with Sheila. Thomas and his twin sisters, Steffy and Phoebe Forrester, eventually gained a stepmother in Ridge's longtime love, Brooke Logan. Thomas, who had also come to depend on Brooke's daughter, Bridget Forrester, was angry when he found out Brooke once had an affair with Bridget's husband, Deacon Sharpe; Thomas downed a whole bottle of vodka and had to be hospitalized.

In high school, Thomas crushed on Caitlin Ramírez, whose father, Hector Ramírez, didn't like rich people. Thomas was relieved when Hector warmed up to him, but soon Thomas had to battle Brooke's son, Rick Forrester, for Caitlin's affections. After Caitlin chose Rick, Thomas started seeing Amber Moore, Rick's ex-wife. Thomas couldn't believe it when Ridge got a restraining order to keep Amber away from him, but Thomas was even more shocked when Amber tried to ruin Ridge's life by getting him to act on his inappropriate feelings for Bridget. Thomas left Amber and reunited with Caitlin.

Thomas bonded with Gabriela Moreno, who had also lost a mother. But after Taylor turned up alive, Thomas campaigned for his parents to remarry. Thomas assured Caitlin she had no reason to be jealous of Gaby, but soon Thomas left Caitlin for Gaby and took a designing job at Spectra Couture, the rival of family design house Forrester Creations, because Forrester denied Thomas an internship. Since Gaby was in the U.S. illegally, Thomas took the advice of attorney Connor Davis and married Gaby in Las Vegas. Thomas accepted Ridge's challenge to a teen fashion showdown; if Ridge won, Thomas had to annul his marriage. Thomas lost the challenge and got the annulment, but made sure Gaby could stay in the country legally.

Thomas went away to college but was furious to learn that Rick had romanced his mother and both his sisters while Thomas was gone. After Phoebe died confronting Rick, Thomas tried to scare Rick into leaving Steffy by setting Rick's house ablaze and blowing up Rick's car. Thomas underwent counseling with James and eventually made peace with Rick, who had broken things off with Steffy. Thomas and Steffy later faked text messages between Ridge and Brooke to make sure Ridge's remarriage to Taylor took place, though Brooke exposed the siblings at the ceremony.

Publishing magnate Bill Spencer, Jr. gained control of Forrester Creations, so Thomas suggested that Steffy seduce Bill to get the company back, later blasting Steffy for doing exactly that when Steffy also tried to blackmail Brooke. Thomas stuck up for Brooke in a meeting and included her in an idea to revive her men's line. To call attention to the collection, which Thomas renamed Taboo, Thomas kissed his sometime stepmother on the runway when PR whiz Whip Jones suggested Thomas pull a publicity stunt, which enraged Taylor. Thomas became fascinated with Brooke and kissed her as she slept, even though he was dating Dayzee Leigh.

En route from a Taboo promo tour, Thomas and Brooke nearly died in a plane crash and were stranded on a deserted island. Forced to eat hallucinogenic berries to survive, Thomas wasn't sure if he'd actually slept with Brooke or just imagined it. Once home safe, Thomas accepted a bribe from his grandmother, Stephanie Forrester: if Thomas would help keep Ridge and Brooke apart by lying that Brooke had sex with Thomas on the island, Thomas would earn Stephanie's 25% share in Forrester. Thomas nearly went through with the plan but came clean after Dayzee begged him to; Thomas lost both Dayzee and Taboo and found himself "banished" to the Forrester basement with Thorne, who wondered if Thomas might be gay.

Thomas took an interest in Brooke's daughter, Hope Logan, and whisked Hope off to Cabo San Lucas, where Steffy happened to be vacationing with Hope's ex-fiancé, Liam Cooper. Thomas worked with Steffy to keep Hope away from Liam, but the scheme backfired. Later, Thomas competed with Rick for the attentions of Caroline Spencer, who had two mothers, Karen Spencer and Danielle. Thomas wholeheartedly accepted Karen and Danielle's relationship, and later helped Caroline clear their buddy Marcus Forrester, who thought he had hit Dayzee's friend Anthony with his car while texting. Thomas remained conflicted about Hope and kissed her twice, but ultimately chose to stay with Caroline.

After Thomas became interim CEO of Forrester in Ridge's absence, Thomas butted heads with Rick, who wanted Caroline for himself; Thomas lost Caroline when Rick crashed through a second-story window because of their argument. After Stephanie died of lung cancer, Thomas was ready to use the 25% share Stephanie promised him to implement his new ideas, but Stephanie left behind a DVD that ultimately transferred all CEO power to her widower, Thomas' grandfather Eric Forrester. Thomas had to battle Rick in a fashion showdown for the presidency of Forrester, which Rick won.

Thomas hit the runway with other male Forrester executives for Caroline's cancer foundation fundraiser. Later, Thomas moved into his childhood beach house and roomed with his friend, Oliver Jones. Thomas became a sounding board for Steffy and Taylor, then failed to convince Eric that Thorne would make a better president than Rick. Thomas eventually moved to Paris to work with Thorne at Forrester International and watched as his cousin, Aly Forrester, had an unusually intense negative reaction to Hope's boyfriend, Wyatt Fuller.

Thomas agreed to sign his 5% stake in Forrester over to Ridge, who wanted to combine his stock with Steffy's and Bill's to overthrow tyrannical CEO Rick. After Aly, who had a history of mental illness stemming from the tragic childhood loss of her mother, died in a confrontation with Steffy, Thomas came home for Aly's memorial. Thomas still had feelings for Caroline, who had moved on with Ridge; when Ridge suddenly dumped Caroline because he couldn't give her the family she wanted, Thomas' comforting turned to lovemaking after too much wine. Thomas was taken aback when Caroline didn't remember sleeping with him because she had also taken antianxiety pills; Thomas swore he wouldn't have initiated sex if he'd realized she'd been so incapacitated. Thomas and Caroline agreed to forget the evening ever happened.

Thomas became a womanizer, kissing Forrester intern Nicole Avant and bedding a bevy of other girls; after Ridge blasted Thomas for crossing the line with co-workers, Thomas punched Ridge, which got him shipped back to Forrester International. When Thomas came back, he found out Caroline was pregnant; satisfied to hear the child was Ridge's, Thomas moved in on Wyatt's girlfriend, Ivy Forrester, and bet Steffy he could get Ivy into bed. Thomas and Wyatt blamed each other when Ivy was electrocuted during an argument with Steffy, who had told Wyatt about Thomas and Ivy's kisses.

Thomas gave up playing around and felt a strong connection when Caroline gave birth to baby Douglas, whom Ridge had named in honor of Stephanie's maiden name. But when Ridge announced that Thomas was really Douglas' father, and that Caroline had known all along, Thomas briefly took off with Douglas, eventually agreeing to let Ridge raise Douglas to avoid a scandal. After Caroline split from Ridge, Thomas offered to raise Douglas with her, but Caroline declined, so Thomas befriended Nicole's half-sister, Sasha Thompson, and defended her from her bullying father, Julius Avant. Thomas built on Sasha's thank-you kiss by dating her though he still felt pulled toward Caroline. When Sasha didn't want to come between Thomas and his son, Thomas went on an extended trip to New York with Caroline and Douglas, but returned alone, reporting that, while he and Caroline had tried to make a go of things, their relationship was up in the air.

Thomas met feisty fledgling designer Sally Spectra, the namesake grand-niece of Spectra Fashions knockoff queen Sally Spectra; he couldn't help but laugh when Sally started a food fight with Steffy. When Sally thought Thomas was insulting her designs, he silenced her with a kiss. At the wedding of his cousin, Zende Forrester Dominguez, Thomas spotted the uninvited Sally dressed as a caterer and gently warned her to leave, but later Thomas was amused to see a video on social media showing Steffy shoving Sally's face into a cake. Running into Sally at Steffy's wedding to Liam in Australia, Thomas told Sally that he would have taken her as his date had he known she was going to be there. After Sally's squabble with Steffy ended with Sally falling into Manly Harbour, Thomas jumped in after her and kissed her.

Thomas couldn't understand it when Sally dumped him for not telling her he had a son with Caroline, yet proudly attended Spectra's premiere showing. When he saw Forrester designs sashaying down their runway, Thomas agreed Sally should be prosecuted, but spoke up for Sally at her hearing. After Thomas learned that Bill had been actively sabotaging Spectra so he could buy the building and replace it with a skyscraper, Thomas invested $100,000 in Spectra, then became its lead designer after Ridge fired him from Forrester. Thomas and Sally affirmed their feelings for each other and finally made love, assuring a dubious Steffy that Sally wasn't simply using him to revitalize Spectra.

Thomas turned Forrester's swimwear showing in Monte Carlo into a fashion duel with Spectra. When Caroline returned to town with Douglas, Thomas railed against Bill's demand that Thomas take Caroline back, but reeled after he learned from Bill that Caroline was dying. Thomas gently told Sally he needed to spend Caroline's last days with her and their son. After several weeks in New York City, Thomas returned to L.A. upon hearing that Spectra had burned to the ground and that Sally had suffered minor smoke inhalation; Thomas expressed his love for Sally, but stayed with Caroline and Douglas.

Months later, off-screen, Thomas learned that Caroline wasn't dying after all, and never had been; it had all been a scheme of Bill's. Thomas returned to L.A furious with Bill and was briefly suspected of shooting Bill in the back. Thomas apologetically explained everything to Sally and offered to take her and her Spectra crew to New York with him to reboot Spectra Fashions in the Big Apple despite being warned by the police not to leave town until the identity of Bill's shooter had been discovered. Later, it was said that Thomas took Sally back to New York, only to dump her for Caroline.

In 2019, Thomas came home with Douglas and the sad news that Caroline, with whom he'd been living as co-parents after their romantic relationship fell apart, had died of a sudden blood clot. Seeing that his child was without a mother, and Hope, who had recently lost Liam's baby, was without a child, Thomas set about trying to break up Hope's marriage to Liam so he could have Hope for himself. Thomas noted Hope and Douglas' newfound closeness and forged a drawing from his son for her; then, with Liam out of town, Thomas kissed Hope and proposed to her, facing Hope's refusal.

Thomas became increasingly unstable in his pursuit of Hope as he forged a deathbed letter from Caroline to convince Hope she should be a mother to Douglas. Thomas discovered that Hope's OB/GYN, Reese Buckingham, had put a dead infant in Hope's arms and given her own baby, Beth, to Steffy to adopt so he could pay off gambling debts. But when Thomas saw Steffy and Liam functioning as a family, he kept quiet about the identity of “Steffy's” daughter. Thomas menaced Reese's daughter, Zoe Buckingham, her boyfriend, Xander Avant, and Reese's accomplice, Flo Fulton, who all knew the truth, into keeping their mouths shut as well. When Xander's ex-girlfriend, Emma Barber, learned that Hope's baby was alive, Thomas tailed Emma down a dark road as she drove to Hope's and watched as Emma's car crashed through a guardrail and rolled down an embankment. Thomas feigned shock when Hope reported that Emma had died and scoffed at Xander and Flo's notion that he had killed Emma, yet privately recalled that he'd only been trying to get Emma to pull over when the accident happened.

After Hope got an annulment from Liam, Thomas spiked Liam's drink with an aphrodisiac he'd gotten from his best friend, Vinny Walker, so Liam and Steffy would make love. Thomas coached Douglas to propose to Hope on his behalf, then projected a ghost image on the wall to frighten Douglas, knowing Hope would want to become his son's mother right away. When Douglas found out Steffy's baby was really Hope's, Thomas threatened to abandon Douglas if he squealed. However, after whisking Hope away on a "staycation," where Thomas hoped to finally get his reluctant bride into bed, Thomas learned that a defiant Douglas had told Liam that Hope's baby was alive.

Thomas abruptly arranged to take Hope away in a helicopter, dragging her out of Forrester when Liam tried to tell Hope the truth. On the Forrester roof, Thomas and Liam had a fistfight that ended with Thomas wordlessly confirming that he had married Hope knowing that her baby with Liam wasn't dead. Thomas escaped and hid out at his friend Vinny's apartment, where he raged about Douglas stabbing him in the back. Believing he could win Hope back if he could get her alone to explain things, Thomas confronted Hope, but fell over a cliff when Brooke pushed him away from her. In the hospital, Thomas admitted to Ridge that he had left Emma to die. When Ridge protected him from the police, Thomas swore to be a better person and was said to be receiving counseling in off-screen phone calls with Taylor.

Thomas was dubious at first when Hope decided to spend time with him and Douglas, but Thomas' feelings for her resurfaced, and he considered signing papers giving Hope joint custody if she slept with him. When he found out Hope was playing him, Thomas chased Hope and fell into a vat apparently filled with acid. But Thomas had only fallen into water and pretended to be dead so Hope would know what it was like to keep a dark secret, the way he had about Beth. Later, Thomas told Liam that he was looking at his executioner, later downplaying the threat to Hope and Steffy.

To keep Hope from remarrying Liam, Thomas got Steffy to kiss Liam, made sure Hope saw it, and began seeing Zoe to make everyone believe he was over Hope. Thomas used Douglas' anxiety over the possibility of being taken away from Hope to get under Hope's skin. And badgered the boy to tell Hope she should let Thomas marry her instead. Thomas designed wedding dresses for both Zoe and Hope and left Zoe at the altar when Hope arrived wearing his gown, only to learn Hope, Zoe, Liam, and Steffy had tricked him into revealing his continuing obsession with Hope. Earning the disgust of Hope and his family, Thomas ran out of the ceremony in tears and went rogue.

A calmer Thomas was on hand to support his sister, Steffy, after she had been injured in an automobile accident. Thomas was again said to be receiving counseling from Taylor, and took work calls, though he apparently wasn't working at Forrester. Thomas inadvertently aided Steffy's addiction to painkillers by bringing her a care package from Vinny, not knowing Vinny had stashed illegal pills inside. Thomas tried to convince Hope he was getting better and asked to be reinstated on the Hope for the Future line, becoming frustrated when Hope gave the position to the returning Zende instead. Thomas took a mannequin of Hope home and questioned his sanity when it began "talking" to him. Thomas struggled to resist “Hope's” demands to take Hope for himself and kill Liam, but managed to stay above concerns about his health, even after Liam discovered the mannequin in Thomas' apartment.

Thomas fainted and hit his head, causing the mannequin to become so real to him, it seemed to move independently. One night, after slipping during a dinner with Douglas and telling the real Hope that he'd like to be a family with them again, Thomas caught himself kissing the Hope mannequin. Arguing with it in front of Hope, Thomas collapsed and required surgery to correct bleeding in his brain, which had been triggering his hallucinations.

Thomas supported Hope's marriage even after he learned that Liam had seen Thomas kissing the mannequin and slept with Steffy, thinking Hope had betrayed him. Even after it turned out Steffy was pregnant and unsure if Liam or Steffy's new boyfriend, John "Finn" Finnegan, was the father, Thomas encouraged Hope to forgive Liam and ignored Vinny's insistence that Thomas now had a chance with Hope. After Thomas learned that Vinny was working as a lab tech and had access to Steffy's paternity test, Thomas began to suspect that Vinny had altered it to read that Liam had fathered Steffy's child instead of Finn. Thomas confronted and got punched in the face by Vinny, who confessed he'd tampered with the test to free Hope up for Thomas.

Thomas shunned Vinny, but was devastated when he got a call to identify a body in the morgue; it was Vinny, who had been left for dead in a hit-and-run. Thomas swore he'd make Vinny's killer pay, only to find himself questioned by the police, to whom Thomas revealed Vinny's habit of drug dealing. The indignant Thomas was glad when Liam went to jail for hitting Vinny, and when Bill followed for covering it up, but Thomas mellowed when Liam asked him to watch over Hope, though Thomas got a talking-to from Ridge to ensure Thomas' obsession with Hope wouldn't flare back up. After Zende helped Thomas reboot his uncooperative phone, Thomas received a slew of texts from the departed Vinny, including a video in which Vinny filmed himself stepping in front of Liam's car to frame Liam and clear the way for Thomas with Hope. Thomas went to Bill's lawyer and right-hand man, Justin Barber, with his evidence that would free Liam and Bill, but Thomas took a punch from Justin and woke up in a makeshift cage; it turned out Justin was taking advantage of Bill's incarceration to seize control of Spencer Publications. Thomas went straight to the police after Hope freed him with a crowbar, which led to Bill and Liam being released from jail.

Thomas became intrigued with Zoe's sister, Paris Buckingham, and arranged to have her sublet the apartment he had taken over from Vinny, since Thomas was buying a house. But when the sale fell through, Thomas agreed to share the apartment with Paris, which didn't sit well with Paris' boyfriend, Zende. Thomas made a move on Paris, only to get rejected in favor of Zende. Later, Thomas was overjoyed that Taylor had moved back to town after a multi-year absence, and he began to agree with Steffy that Ridge should leave Brooke for Taylor. Thomas got an earful from Douglas about the fact that he had seen "Grandma kissing Santa Claus" -- Thomas finally took it to mean that Brooke had kissed Hope's father, Deacon Sharpe, while Ridge was out of town. Thomas supported Ridge when he left Brooke and moved in with Steffy and Taylor, but Thomas took things further when he hid Ridge's phone and kept Brooke from seeing Ridge so she couldn't straighten things out with him.

Thomas was torn when he found out that Finn's mother, Sheila Carter, who had been responsible for Taylor's "death", had switched recovering alcoholic Brooke's alcohol-free champagne with the real thing to sabotage Brooke's marriage to Ridge -- Thomas was appalled by Sheila's actions, but enjoyed the idea of his parents being together again because of them. As Thomas deliberated whether or not to tell the truth, he was horrified to learn that both Steffy and Finn were shot during a robbery, which left Steffy unconscious and Finn dead. Thomas wondered if Sheila had had anything to do with the shooting, but received an emotional denial from Sheila, who balked at the insinuation that she would kill her own son.

After Steffy woke up thinking that Liam was still her husband, Thomas joined his family in gently telling Steffy about Finn. It turned out Thomas had been right to suspect Sheila of the shooting, but Thomas' secret about Brooke's drinking came to light when Sheila confessed to her crimes. Learning that Steffy had only confronted Sheila because Steffy had overheard Thomas talking about the secret, Thomas felt that Steffy and Finn had only been shot because of him. Later, Thomas was relieved when it turned out Finn was alive.

Having been asked by Douglas if Thomas missed Douglas when they weren't together, since they lived apart, Thomas approached Hope about revisiting their joint custody of Douglas and was met with resistance. Undaunted, Thomas got permission to move in with Eric at the Forrester mansion and brought Douglas there for an extended sleepover, refusing to let Douglas go home to Hope. Thomas confessed to Hope that she was the only woman for him and tried to kiss her, then joined Steffy in working to drive Ridge away from Brooke and back to Taylor. While carving an apple, Thomas waved his knife at Brooke and indirectly threatened her; inspired by Brooke's outrage and concern for Douglas, Thomas used a voice-sampling app of Douglas' to fake a phone call to Child Protective Services in Brooke's voice. Thomas reveled in his correct prediction that Ridge would be upset enough to leave Brooke for Taylor.

Just as Ridge and Taylor were set to remarry, Thomas learned that Douglas had told Steffy and Taylor about the voice-sampling app and how Thomas had used it to frame Brooke. Thomas convinced Taylor to stay quiet, but Steffy busted Thomas at their parents' wedding, which led to the ceremony being cancelled. Thomas also found himself without a job when he was ousted from Forrester for his deception. When Hope's fashion line began to falter, Thomas tried and failed to persuade her to bring him back on as a designer. Deciding he wanted Douglas with him full-time, Thomas took Hope to court with the caveat that Douglas choose who he wanted to live with. Thomas was smug when Douglas chose Steffy because he thought it meant having unlimited access to the boy, but Thomas became angry when Steffy set boundaries instead.

After Taylor brokered a peace between him and Steffy, Thomas entered therapy and champed at the bit to accept Steffy's offer to return to Forrester and work on Hope's failing line. At Hope's prompting, Thomas apologized to Brooke as a precursor to Hope agreeing to his rehiring. Thomas was stunned when Douglas suddenly wanted to move back in with Hope and Liam; when Douglas expressed a desire to have both his parents living together all the time, Thomas reminded Douglas that Hope was already married to Liam. Thomas tried to reassure Liam about Hope and pleaded his case to his half-brother, R.J. Forrester, who had just returned home and taken Thomas to task for breaking up Brooke and Ridge, R.J.'s parents.

While working together, Thomas had charged moments with Hope but seemed to be unaware of her growing attraction to him. In Rome for a Hope for the Future showing, Thomas was floored when Hope kissed him. Despite imploring both Hope and Liam to not let what happened ruin their marriage, Thomas began an intensely sexual relationship with Hope after she signed divorce papers from Liam. Thomas insisted he was okay with things the way they were when Hope admitted she didn't reciprocate his love for her and indulged Hope's need to repeatedly be told by Thomas that she was the only woman for him. Thomas took it in stride when Brooke warned him that he was just a phase that Hope was going through. After Xander made a surprise return to town and told Finn about Thomas' part in Emma's death, Thomas was forced to tell Hope that he bore responsibility in that death, though he delivered to Hope an abridged version of events that painted him in a better light. Thomas understood when Hope said she needed time to think.

After Hope confessed to true feelings for him, Thomas proposed to Hope no less than three times; when Thomas received his third rejection, he began to wonder if he had been fooling himself about Hope's level of devotion and received an earful from Steffy, who demanded that Thomas dump Hope. Thomas did break things off with Hope and went to work at Forrester's Paris office to clear his head. Off-screen, Thomas proposed to Paris Buckingham, the sister of his former fiancée Zoe Buckingham, a revelation which came out when Thomas returned home with Douglas. Thomas countered Hope's pleas not to marry Paris by once again asking Hope to marry him, this time as a test of Hope's commitment. When Hope still couldn't say yes, Thomas considered his point proven and asked Eric if he could wed Paris at the Forrester mansion. However, despite getting that permission, Thomas, Douglas, and Paris all returned to France without any wedding taking place.