Objective: To examine the prevalence and changing patterns of PTSD, major depressive episode (MDE), and generalized anxiety disorder (GAD) in adult claimants who sustained a non-catastrophic injury in a road traffic crash (RTC) in Queensland, Australia. Method: Participants (N = 284) were assessed at approximately 6, 12, and 24 months post-RTC using the composite international diagnostic interview (CIDI) modules for PTSD, and CIDI-short form for MDE, and GAD. Results: The prevalence of at least one of these disorders was 48.2%, 52.5%, and 49.3%, at 6, 12, and 24 months, respectively. Comorbidity was common (20.8% at 6 months, 27.1% at 12 months, and 21.1% at 24 months) and only 33.1% of participants never met PTSD, GAD, or MDE criteria. A substantial proportion of participants (42.3%) had an unstable diagnostic pattern over time. Participants with multiple diagnoses at 6 months were more likely to continue to meet diagnostic criteria for any disorder at 12 and 24 months than participants with a single diagnosis. Participants with PTSD (with or without MDE/GAD) were more likely to meet criteria for any disorder at 24 months than participants with another diagnosis. Preinjury psychiatric history increased the likelihood of any disorder at 24 months post-injury, but did not significantly increase the likelihood of PTSD. Conclusions: People injured in a RTC are at risk of having complex psychological presentations over time. Interventions to prevent mental disorders, especially PTSD, in the early post-injury period are needed to prevent chronic psychological injury, including consideration of comorbidity and dynamic course.