Allison Cameron was a member of Gregory House's diagnostic team during the first three seasons; a fellow in Diagnostic Medicine. She returns in the fourth season as the senior emergency room attending physician at Princeton-Plainsboro Teaching Hospital. She is a qualified immunologist. Cameron is portrayed by Jennifer Morrison. She was the youngest member of the team. Her character left part way through Season 6.

Prior to working at Princeton-Plainsboro Teaching Hospital, Cameron was a medical intern at the Mayo Clinic and was one of the top students in her class in medical school.She hails from the Midwestern United States and has a sibling, an unnamed older brother. Cameron worked for House under a medical fellowship alongside Dr. Robert Chase (Jesse Spencer) and Dr. Eric Foreman (Omar Epps) for three years.

At the age of 21, Cameron fell in love with a man, knowing that he had been diagnosed with terminal thyroid cancer. They got married, and six months later her husband died because the cancer had metastasized to his brain.

In House's 1st season, it is shown that Cameron has a crush on House. She resigns in "Role Model", after Edward Vogler forced House to fire one of his team members. When she is asked to return, Cameron only agrees if House will go out on a date with her. The two go on a date in "Love Hurts." Afterward, when they are asked if they will do it again, House replies "I don't think so", while Cameron says she does not know. After seeing House's behaviour when he and his ex-girlfriend Stacy (Sela Ward) reunite, Cameron tells House, "I thought you were too screwed up to love anyone. I was wrong. You just couldn't love me. It’s okay. I’m happy for you."

Cameron sleeps with Chase in season 2 episode 7 (Hunting) while high on drugs, and then begins a "friends with benefits" relationship with him in season 3 at the end of the episode "Insensitive". However, she ended their relationship when Chase informed her that he wanted to take their relationship to the next level. Despite Cameron's refusal to reconcile, Chase starts to ask her out every Tuesday. When she becomes the lone fellow of the Department of Diagnostic Medicine after Chase and Foreman were fired and resigned from their posts, respectively, in the third season finale, Cameron resigns too. Afterward, she goes to Chase's house on a Monday, telling him, "I just didn't feel like waiting".

In season 4 it is shown that Cameron has become a senior attending physician in the emergency room. Chase and Foreman both notice that, despite having resigned from House's team, she is "remarkably involved with his team". Cameron later confides in Foreman that what she misses about her old job is "people doing whatever it takes to get the job done", although she has stated on multiple occasions that she does not want her old job back. Cameron's relationship with Chase moves forward during the fifth season; in the episode "Saviors", after having a little argument with Chase about their canceled vacation, the two get engaged. In "Both Sides Now", the season 5 finale, the two get married.