BACKGROUND: We investigated work-related exposure to stressful and traumatic events in police officers, including repeated exposure to traumatic materials, and predicted that ICD-11 complex PTSD (CPTSD) would be more prevalent than posttraumatic stress disorder (PTSD). The effects of demographic variables on exposure and PTSD were examined, along with whether specific types of exposure were uniquely associated with PTSD or CPTSD. METHODS: An online survey covering issues about trauma management, wellbeing and working conditions was disseminated via social media and official policing channels throughout the UK. In total, 10 401 serving police officers self-identified as having been exposed to traumatic events. Measurement of PTSD and CPTSD utilised the International Trauma Questionnaire. RESULTS: The prevalence of PTSD was 8.0% and of CPTSD was 12.6%. All exposures were associated with PTSD and CPTSD in bivariate analyses. Logistic regression indicated that both disorders were more common in male officers, and were associated independently with frequent exposure to traumatic incidents and traumatic visual material, and with exposure to humiliating behaviours and sexual harassment, but not to verbal abuse, threats or physical violence. Compared to PTSD, CPTSD was associated with exposure to humiliating behaviours and sexual harassment, and also with lower rank and more years of service. CONCLUSIONS: CPTSD was more common than PTSD in police officers, and the data supported a cumulative burden model of CPTSD. The inclusion in DSM-5 Criterion A of work-related exposure to traumatic materials was validated for the first time. Levels of PTSD and CPTSD mandate enhanced occupational mental health services.