〔Abstract〕 To investigate the incidence and influencing factors of posttraumatic stress disorder (PTSD) three months after a traffic accident, and to explore the role of social support and coping strategies. Methods A total of 117 individuals exposed to trauma following road traffic accidents were recruited. General demographic and clinical information was collected within one week, and the hamilton anxiety rating scale (HAMA), the hamilton depression rating scale-24 (HAMD-24), the social support rating scale (SSRS), and the simplified coping style questionnaire (SCSQ) were administered. A 3-month follow-up was subsequently conducted, during which PTSD symptoms were assessed using the post-traumatic stress disorder checklist for DSM-5 (PCL-5). Participants were divided into a PTSD group and a non-PTSD group according to whether PTSD occurred. Between-group comparisons were performed using the Mann-Whitney U non-parametric test or the χ2 test, as appropriate. Spearman’s correlation analysis was used to examine the associations between general characteristics and PCL-5 scores. Binary logistic regression was applied to identify factors influencing PTSD, and receiver operating characteristic (ROC) curve analysis was conducted to evaluate the diagnostic value of the SCSQ and SSRS. Results During the 3-month follow-up of the 117 trauma-exposed individuals, 17 cases developed PTSD, with a higher proportion of females (70.59%). Between-group comparisons showed that, compared with the PTSD group, the non-PTSD group had higher scores for positive coping, objective support, and subjective support (P<0.05), and lower scores for negative coping, HAMA, HAMD, and PCL-5 (P<0.05). Correlation analysis indicated that female gender, negative coping, and higher HAMA and HAMD scores were associated with greater PTSD severity. Logistic regression analysis demonstrated that educational level (OR=1.715, 95% CI: 1.020-2.883, P=0.042) and negative coping (OR=1.590, 95% CI: 1.003-2.522, P=0.048) were risk factors for PTSD, whereas objective support (OR=0.646, 95% CI: 0.451-0.925, P=0.017) was a protective factor. The ROC analysis showed that the total SCSQ score and its negative and positive coping dimensions, the total SSRS score and its subjective and objective support dimensions, as well as their combined use, all demonstrated good discriminative ability in distinguishing between the PTSD and non-PTSD groups. Conclusion The results suggest that individuals who are female, with higher HAMA and HAMD scores after a motor vehicle accident, and those with lower social support and negative coping strategies, should be given particular attention. Early interventions for these individuals may reduce the incidence of PTSD.