Post-traumatic stress was found to be prevalent among New Zealand military personnel in a cross-sectional study of 1817 currently serving and retired military personnel. Experience of significant post-traumatic stress symptoms, defined as scores ≥30 on the Military Post-traumatic Stress Disorder Checklist, were evident for 30% of participants. A further 10% of participants had scores ≥45 indicating a presumptive clinical diagnosis of posttraumatic stress. Lower scores were associated with longer duration of service, ability to adapt to changes in circumstances and good sleep. Higher scores were associated with experience of trauma and were more likely in older males and Māori.