He often hangs around with Turk, his best friend since they were college roommates at the College of William and Mary in Williamsburg, Virginia, and the pair continued to be roommates even as they progressed to become interns and residents. J.D. is often shown to have a codependent fixation on Turk, regularly going through steep depression whenever he can't be with him. In the first episode, when Turk suggests the two of them seek separate apartments to "branch out," J.D.'s inner monologue tells himself to "Tell him you think that's stupid. Tell him you need him."
He meets and connects with Elliot Reid on his first day and finds himself attracted to her. In seasons 1 to 3, a running joke in the series was that J.D. would sleep with Elliot at least once in each season, although the show's producers have indicated that this ended to prevent the characters' development being constrained by clichés. The two form a romantic relationship in My Drug Buddy, which falls apart within two weeks when they realize that they do not work as a couple. J.D. puts his feelings for Elliot to one side until season 3 when Elliot is in a committed relationship with Sean, until Sean is about to move in with Elliot, when J.D. finally declares his love for her, claiming, "It should be me", and she leaves Sean for him. However, J.D. realizes that after chasing her for three years, he no longer wants to be with her, a heartbroken Elliot is initially furious with J.D., but they do reconcile and later they realize they have lost all romantic feelings. It is not until near the conclusion of season 6 that their relationship appears to rekindle, the episode "My Point of No Return" ends with J.D. and Elliot lying on a bed in the On-Call room, leaning in for a kiss. The action remains unresolved until season 7, where Elliot backs out as JD 'kisses air'. They both then say that the almost-kiss had nothing to do with their feelings for each other. He also meets Carla, a nurse who advises him and affectionately nicknaming him "Bambi". The Janitor decides to spend most of his time torturing J.D. with elaborate plans that sometimes backfire on himself. He has romantic liaisons with various women, besides Elliot, including Kim, the mother of his child, Sam Perry Gilligan Dorian. J.D.'s apparent mentor at Sacred Heart is Dr. Perry Cox, who generally refers to J.D. as "Newbie" or by a series of girls' names, a pastime he reserves especially for J.D. As much as he doesn't admit it, it has been revealed that Cox respects J.D. as a doctor, heeds his advice, respects his opinion, and even cares about him as a person. In the episode "My Fallen Idol," J.D. initially refuses to visit Cox at his apartment when the latter has a breakdown following the death of three patients in the previous episode. He claims that he doesn't approve of Cox showing up to work drunk, but later confesses to Cox that he still looks upon him as a hero, and that seeing him being so affected by his job scares him. J.D tells Cox that he (Cox) is the kind of doctor he (J.D.) wants to be. The defining moment of their relationship occurs at the end of "My Fallen Idol" where Dr. Cox thanks J.D., for helping him escape from severe depression.
J.D.'s most prominently featured quirk is his habit of daydreaming. When this happens, he tilts his head back and to the left, blankly looking upwards. The sequences played out in his daydreams are of surreal scenarios and situations that have just been mentioned or wondered about, often in an exaggerated manner. Despite his numerous flaws, quirks and personal insecurities, J.D. is shown throughout the series to be a very competent doctor. While he doesn't possess as much technical knowledge about medicine as Elliot, he is described by Carla and Dr. Cox as having "very good instincts" and a lot of determination and enthusiasm for his job.