OBJECTIVE: To identify factors that predict running ability following traumatic brain injury (TBI), and to quantify performance thresholds for these predictors. DESIGN: Cross-sectional cohort study. PARTICIPANTS: One hundred fourteen people with TBI. OUTCOME MEASURES: Self-selected walking speed, the high-level mobility assessment tool, postural stability (lateral center of mass displacement), ankle power generation at push-off and quality of gait performance (Gait Profile Score). RESULTS: All predictor variables were all strongly associated with the ability to run. However, only self-selected walking speed contributed significantly to the final result. Investigation of performance thresholds for self-selected walking speed indicated that following TBI, people who walk at speeds of 1.0 m/s or higher are 16.9 times more likely of being able to run than for those who walk at speeds of less than 1.0 m/s. CONCLUSIONS: Self-selected walking speeds higher than 1.0 m/s greatly increase the likelihood of running following brain injury. The 1.0 m/s threshold, although slower than able-bodied self-selected walking speeds, may be an important indicator of the ability to run in this population.