Objective. This study aimed to determine the incidence, prevalence, and progression of temporomandibular joint (TMJ) magnetic resonance (MR) imaging findings and symptoms in patients over a 15-year period after whiplash trauma, compared with control participants. Study Design. Sixty consecutive patients were enrolled directly after whiplash trauma. The study protocol included TMJ MR imaging at inception and 15 years later, as well as a questionnaire and interview at inception, at 1-year follow-up, and at 15-year follow-up. Fifty-seven patients (95%) participated in all three examinations (85% for MR imaging). Fifty matched control participants were examined. Results. The prevalence of TMJ symptoms was significantly higher in patients compared with control participants at inception (44% vs 20%, P = .0055) and remained significantly higher throughout the study period. The prevalence of disk displacement did not differ significantly between groups either at inception (63% vs 53%) or at 15-year follow-up (63% vs 55%). Conclusions. This prospective 15-year follow-up suggests that the development of TMJ symptoms, both immediate and delayed, is common in whiplash patients.