OBJECTIVES: The BRAIN-Q is a tool aimed at maximising the accuracy and minimising measurement error for retrospectively assessing concussions. This paper reports the agreement of the BRAIN-Q tool when compared to extant questionnaire questions, and its reproducibility when compared with its telephonic version (tBRAIN-Q). METHODS: The BRAIN-Q entails a 3-stage process: defining a concussion, creating a visual timeline with life events, and establishing detailed characteristics for each reported concussion. It was designed to be administered in-person by trained personnel, and was used in the BRAIN study. Its performance was compared with the MSK study, which previously collected a few questions in a broader self-administered questionnaire, and with the tBRAIN-Q Recall, its telephonic version. RESULTS: In total, 101 participants were included, of whom 9 were re-assessed with the tBRAIN-Q. The agreement of the BRAIN-Q with the muscle skeletal-questionnaire for rugby-related concussion was 86.7% (κ=0.6). Rugby-related concussion with loss of consciousness showed lower agreement (82.0%; κ=0.6). The comparison between the BRAIN-Q and the tBRAIN-Q showed good reproducibility. CONCLUSIONS: The BRAIN-Q is a relatively easy tool to administer in face-to-face assessments, and it showed optimal reproducibility. It includes a well-established definition of concussion, and is used to collect detailed information on each concussion, allowing for a number of subgroup analyses (e.g., by severity, age, or context). The BRAIN-Q is easily adaptable to other sporting settings.