OBJECTIVES: Posttraumatic stress disorder (PTSD) is a disabling mental health condition arising from experiencing serious traumatic events. This study investigated if PTSD secondary to the World Trade Center terrorist attack on 11 September 2001 (9/11) is associated with self-reported doctor's diagnosis of periodontitis and count of missing teeth. METHODS: Data from the World Trade Center Health Registry, 2003-2020 (n = 20 826) were used to prospectively examine the rate of periodontitis and cross-sectionally the odds of missing teeth among enrolees with/without PTSD post-9/11 using a modified Poisson regression and generalised logit model, respectively, adjusted for covariates. RESULTS: Approximately 17% reported a doctor's diagnosis of PTSD post-9/11 and 7.4% a doctor's diagnosis of periodontitis. There were 355 new cases of periodontitis (incidence rate = 7.6 per 1000 person-years) among those with PTSD and a rate of 4.3 per 1000 person-years among those without PTSD. The covariate-adjusted rate ratio for periodontitis comparing those with and without PTSD = 1.52 (95% CI: 1.33, 1.74). The adjusted odds ratio (OR) (95% CI) comparing those with and without PTSD were, respectively, OR = 1.15 (95% CI: 1.05, 1.25) and OR = 1.41 (95% CI: 1.09, 1.83) for missing 1-5 teeth and all teeth missing, respectively, as compared to no missing teeth. CONCLUSIONS: PTSD post-9/11 appears to be associated with poorer oral health outcomes, underscoring the far-reaching consequences of traumatic events on oral health.