1995–2005

When Luke was born, his mother Lily Walsh did not know whether his father was her then-spouse Damian Grimaldi or her lover Holden Snyder. Although Damian proved to be the father, the two men struggled over possession of the boy for years before Holden – who had married Lily some years earlier – adopted Luke. When Luke was a teenager, he confessed to the murder of Julia Larrabee, who he blamed for breaking up his parents' marriage, to protect his mother, who he thought was guilty of the crime. When the true killer was found to be somebody else, his life did not return to normalcy; as his mother began dating another man, Keith Morrissey, Luke became an alcoholic. Following her son's kidney failure, Lily was blackmailed into promising to marry Keith by his promise of a new kidney for Luke, but after Luke's passionate appeal to Keith he released her from her vow. Luke's family was left intact, but Luke's problems were not over, as he continued seeing destructive friends and accidentally hit a pedestrian, Jade Taylor, with his car.

2005–07

Luke trusted Jade, who claims to everyone that she is Luke's cousin, enough to reveal his deepest secret to her – his romantic love for Kevin – she turned out to be a fraud, forcing him to pretend to be in love with her. Unfortunately, this destroys his relationship with Kevin. A desperate Luke comes out to his friend Will Munson before, on Will's advice, revealing his secret to his family. While a pregnant Lily can't accept her eldest son's sexual orientation, the rest of his family supports him.

Shortly after his surprise reappearance in their lives, Luke's birth father Damian tries to send Luke to a gender re-alignment camp. When Lily realizes the nature of the camp, she tries to reassure Luke that she will accept him, but thinking her the sole responsible party he lashes out angrily at her for her betrayal, inadvertently knocking her down the stairs. She lapses into a coma. Holden will not accept Luke's explanation for what happened, and Luke takes shelter from his adoptive father's anger with Damian. He grows closer to Damian especially when Damian claims to be dying...but it all falls apart when he later discovers the truth of his father's health. He severs ties with his birth father, changing his name, but yields his share in the Grimaldi family fortune to Damian before he goes.

Back home, Luke comes out to his friends. While Kevin has difficulty at first, he reconciles with Luke after Luke saves his life. Lily, who gave birth while in her coma, finally emerges to also reconcile with Luke and, to everyone's surprise, Jade turns out not to be a fraud after all.

2007–10

While interning at WOAK, Luke meets and falls for Noah Mayer. Noah is dating Luke's friend Maddie Coleman, but soon after Luke reveals his feelings to Noah, he begins to struggle with his own attraction. Eventually, he acknowledges that he is also gay, although he fears revealing this to his father. Unfortunately, Colonel Mayer learns the secret when he catches them in their second kiss and rejects Noah before devising a plan to murder Luke. His efforts leave Luke paralyzed for a time, although physical therapy, and Noahs help, eventually put him back on his feet. In spite of Colonel Mayer's plans, he and Noah remain a couple.

Their relationship is challenged when Noah, to save a young Iraqi woman with connections to his father from deportation, decides to marry her. Although he weds Ameera Ali Aziz, Noah reassures Luke of his steadfast love, but the relationship eventually instigates a break-up of the pair after Colonel Mayer is seemingly killed in a kidnapping plot and Ameera arrested. Noah blames Luke for the events, and Luke is angry that Noah requests time apart. The pair reconcile after a visit from Cyndi Lauper, who dedicates a performance of the song "True Colors" to them.

When Damian returns a portion of Luke's inheritance to him, he decides to start a charitable foundation, run by Brian Wheatley, who encourages Luke to be more discreet in his homosexuality to avoid alienating the philanthropic community. He also enters politics, running against his old friend Kevin for President of the Student Government at Oakdale U. He winds up cheating to overcome a dirty campaign by Kevin and is expelled when Noah comes clean to the dean about what Luke did. After an angry Luke, and Noah break up during the fallout, he begins drinking again and while drunk is kissed by Brian, who has married Luke's grandmother Lucinda. Later, when Luke is living at Lily and Holden's house and Brian and Lucinda must come to stay with them, does Brian confess that, he is attracted to Luke, and loves Lucinda.

Luke and Noah begin to rebuild their relationship after the election scandal, and reunite by Christmas, but when Luke becomes paranoid and jealous of Noah's friendship with Maddie, he kisses Brian himself. Noah, who sees this, is angry with Luke for some time, and Lucinda is soon angry as well when Jade blurts out the secret. Ostracized, Brian comes very close to suicide before Luke and Noah can intervene, but after their intervention, he makes peace with Lucinda and his own homosexuality before leaving town. Also, with the help of Jade, Casey Hughes, and Lucinda, Luke and Noah get back together and finally consummate their relationship.

Luke turns his Luke Snyder Foundation to LGBT rights after he and Noah are discriminated against in their housing search, but his personal life is complicated when Damian returns, ostensibly to make amends. Then, when a couple, under the guise of being twins, that Luke takes on as volunteers for his Foundation prove to be con-men after money, kidnapping first Noah and then Luke. Damian saves them both. Damian eventually remarries Lily, after Holdens apparent death, but flees the country mysteriously soon after.

When Noah is blinded in an accident at film school, he grows distant with Luke, feeling a need to be independent and continuously holding Luke responsible for what happened. Tired of being pushed away and blamed for Noah's accident Luke ends things with Noah, although Luke continues to help Noah during his crises, and they maintain a rocky friendship. Luke becomes intrigued by neurosurgeon Reid Oliver, who is working to save Noah's sight after Luke bribes him to come to Oakdale on Noahs behalf. Their involvement starts out a bit rocky when Noah gets his sight back, and refuses to reunite with Luke after seeing him and Dr. Oliver kissing. Feeling loyalty toward Noah, and guilt for falling for his doctor, Luke has a hard time figuring out who he wants to be with, in most cases, rebuking the Dr.s advances. In the end, however, he decides to pursue his relationship with Reid, with Noah remaining a constant presence. Soon after, Noah receives a grant to make a movie in Los Angeles and asks Luke to go with him. He tells him he cannot go. During the final episodes, Reid is mortally injured when his car is struck by a train.

With Reid dying not long before he is set to leave for LA, Noah is convinced by Allison to comfort Luke, but while he is willing to remain in Oakdale during his time in need, Luke urges him to pursue his dream. Noah tells Luke to stay in Oakdale, grieve, and heal, and that he will be waiting for him, leaving the door open to reconciliation. Noah leaves and Luke continues to grieve Reid. In his last scene Katie, Reid's best friend and roommate, gives Luke his stethoscope saying Reid would want him to have it. Luke asks Chris, the man who received Reid's heart after he died, if he could use it to listen to his heartbeat. He says it's okay and the final shot we ever have of Luke is of him listening to Reid's heart with a sad smile on his face.