James Wilson is House’s closest friend and the head of oncology in House M.D.
Wilson works at Princeton-Plainsboro Teaching Hospital and regularly supports House despite frustration with his behavior. As an oncologist, he brings expertise in cancer diagnosis and treatment, while his empathetic style contrasts with House’s hostility and rule-breaking.
Their friendship is one of the show’s enduring relationships. Wilson often challenges House’s assumptions, helps interpret his motives, and acts as a moral counterweight. House, in turn, relies on Wilson more than he admits. Their arguments can be serious, but the series repeatedly returns to their loyalty and shared history.
The character’s full name is James Evan Wilson, and he is played by Robert Sean Leonard. That distinction matters because “James Wilson” is the fictional doctor, while “Robert Sean Leonard” is the actor. Wilson’s specialty is oncology, not diagnostic medicine, although he frequently participates in diagnostic cases.