Objective: To determine incidence of injury and to identify risk factors among Brazilian Jiu Jitsu (BJJ) fighters at an international level tournament. Design: Prospective Observational Cohort Design. Setting: 2011 World Brazilian Jiu Jitsu Championships. Patients: A cohort of 2165 BJJ male and female fighters were prospectively monitored during the 2011 World Brazilian Jiu Jitsu Championships. Data collected were injury incidence of belt rank level and baseline characteristics of previous history of injury, prior years’ experience, number of days training, injury experience, injury severity, and subsequent time-loss. Incidence rates (IR) per 1000 Athletic Exposures (AEs) were captured of belt rank and injury location, in addition to relative risk (RR) to gather comparisons of fighter previous history, injury joint location, and gender. Main Outcomes: Injury Incidence and Relative Risk. Results: The cumulative injurty incidence rate for BJJ during the championships was 31.8/1000AEs. Blue belt level had highest injury incidence; 34.1/1000 AEs followed by white belt 35.1, purple belt 21.2, brown belt 20.2, and black belt 19.3. The elbow joint was the higest reported incidence of injury; 10.4/1000 AEs. Injury rates did not differ significantly by gender; IRR 1.04. Fighters who reported a previous history of injury were three times more likely to be injured during the event RR 3.1. Additionally, fighters who reported a previous history of elbow joint trauma were two times more likely to sustain another elbow injury during the event; RR2.2. Conclusions: Findings suggest that previous history of injury is a risk factor among fighters at an international BJJ competition. Specifically, elbow joint previous history may increase risk of sustaining an additional elbow injury at a large scale BJJ event. Lastly, there were no significant differences among injury between gender.