Objective To characterize risk factors for and consequences of posttraumatic stress disorder (PTSD) among older adults evaluated in the emergency department (ED) following motor vehicle collision (MVC). Design Prospective multicenter longitudinal study (2011–2015). Setting 9 EDs across the United States. Participants Adults aged 65 years and older who presented to an ED after MVC without severe injuries. Measurements PTSD symptoms were assessed 6 months after the ED visit using the Impact of Event Scale-Revised. Results 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% vs. 30%), functional decline (67% vs. 42%), and new disability (49% vs. 18%). Conclusions 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.