This cross-sectional analysis investigated the association between posttraumatic stress disorder (PTSD) and social inhibition (SI). A total of 1232 individuals aged 32-71 years with a history of traumatic experience were identified from the population-based Cooperative Health Research in the Region of Augsburg F4 study conducted in 2006-2008. PTSD was assessed by the Impact of Event Scale, Posttraumatic Diagnostic Scale, and interview data. SI was measured by the SI subscale of the German version of the Type-D scale and dichotomized in a high (score of ≥10) and nonhigh group. Even in the fully adjusted multinomial logistic regression model (adjusted for age, sex, sociodemographic and metabolic risk factors, anxiety, depression), high levels of SI were significantly associated with PTSD (partial: odds ratio, 1.58; 95% confidence interval, 1.19-2.09; p = 0.002; full: odds ratio, 2.45; 95% confidence interval, 1.25-4.82; p = 0.009). Our findings suggest a dose-response relationship between PTSD and SI and should be integrated in individual therapy plans, especially of patients with interpersonal violence experience.