Motor vehicle collisions (MVCs) are a common source of traumatic stress, which could lead to the development of posttraumatic stress disorder. However, the natural course of symptom development is still poorly understood. The current study aimed to prospectively examine the expression of traumatic stress symptoms in mild-moderate injured MVC survivors, using a novel daily life repeated measurement approach. Participants (N = 70) were screened and recruited upon hospital arrival. Daily assessments of traumatic stress symptoms were conducted via mobile phones, and the data during days 2-6 (acute phase) and 27-31 (1-month phase) following the MVC were used for the current study. Latent growth curve analyses showed that at the acute phase, traumatic stress symptoms followed a reducing trajectory, with significant intercept and negative slope factors. At the 1-month phase, traumatic stress symptoms followed a low-stable trajectory, with a lower intercept and a nonsignificant slope factor. The acute-phase intercept and slope were both positively associated with 1-month symptomatology, such that higher initial symptoms and slower recovery rates were associated with greater traumatic stress symptoms at 1-month post-MVC. Trauma history and peritraumatic perceived life threat were indirectly associated with the 5-days end-of-the-month traumatic stress symptoms, through the mediation of the acute-phase intercept. An early screen of traumatic stress symptoms in the first few days following trauma exposure, together with trauma history and perceived peritraumatic life threat, may assist in identifying individuals at risk for subsequent posttraumatic psychopathology. (PsycInfo Database Record (c) 2022 APA, all rights reserved).