INTRODUCTION: The United States has been actively involved in major armed conflicts over the last 15 years. As a result, a significant proportion of active duty service personnel and returning veterans have endured combat, putting them at risk for developing post-traumatic stress disorder (PTSD), a disabling disorder that may occur after exposure to a traumatic event. Current therapies often require long-term, time-intensive and costly commitment from the patient and have variable degrees of success. There remains an ongoing need for better therapies, including complementary medicine approaches that can effectively reduce PTSD symptoms. While anecdotal evidence suggests that routine practice of Brazilian Jiu Jitsu (BJJ) can reduce symptoms of PTSD, there have been no formal studies to address this. MATERIALS AND METHODS: This study was approved by the University of South Florida Institutional Review Board (#PRO00019430). Male US active duty service members and veterans from the Tampa area participated in a 5-month (40 sessions) BJJ training program. Before beginning and again midway through and upon completion of training the participants completed several validated self-report measures that addressed symptoms of PTSD and other co-morbid conditions. Effect size and 95% confidence intervals were determined using a within-person single-group pretest-posttest design. RESULTS: Study participants demonstrated clinically meaningful improvements in their PTSD symptoms as well as decreased symptoms of major depressive disorder, generalized anxiety and decreased alcohol use; effect sizes varied from 0.80 to 1.85. CONCLUSIONS: The results from this first-of-kind pilot study suggest that including BJJ as a complementary treatment to standard therapy for PTSD may be of value. It will be necessary to validate these promising results with a larger subject cohort and a more rigorous experimental design before routinely recommending this complementary therapy.