To characterize risk factors for and consequences of post-traumatic stress disorder (PTSD) among older adults evaluated in the emergency department (ED) following motor vehicle collision (MVC). Prospective multicenter longitudinal study (2011-2015). 9 EDs across the United States. Adults aged 65 years and older who presented to an ED after MVC without severe injuries. PTSD symptoms were assessed 6 months after the ED visit using the Impact of Event Scale-Revised. Of 223 patients, clinically significant PTSD symptoms at 6 months were observed in 21% (95% CI 16%-26%). PTSD symptoms were more common in patients who did not have a college degree, had depressive symptoms prior to the MVC, perceived the MVC as life-threatening, had severe ED pain, and expected their physical or emotional recovery time to be greater than 30 days. Three factors (ED pain severity 0-10 scale, perceived life-threatening MVC 0-10 scale, and pre-MVC depressive symptoms yes to either of two questions), predicted 6-month PTSD symptoms with an area under the curve of 0.76. Compared to patients without PTSD symptoms, those with PTSD symptoms were at higher risk for persistent pain (72% versus 30%), functional decline (67% versus 42%), and new disability (49% versus 18%). Among older adults treated in the ED following MVC, clinically significant PTSD symptoms at 6 months were present in 21% of patients and were associated with adverse health outcomes. Increased risk for PTSD development can be identified with moderate accuracy using information readily available in the ED.