This is the first study to assess sport concussion knowledge and the effect of sport concussion self-report on knowledge in the UK general public. In the online survey, participants (n = 227) stated personal sport concussion history, injury indicators, and rated 26 injury statements for truthfulness using definite (true, false) or non-definite (probably true, probably false) response options. As anticipated, knowledge was limited. Few statement ratings were definite, and misconceptions prevailed. The injury's seriousness was systematically underestimated, suggesting that knowledge may not be sufficient for injury self-diagnosis and self-recovery measures. Sport concussion self-report was associated with more definite than non-definite statement ratings. However, response accuracy did not differ. This suggested that personal injury experience may yield a false sense of security. The use of accessible, easy-to-use tools needs to be promoted to improve sport practice safety.