Background: The research literature was systematically reviewed and results were summarized from studies assessing bicycle helmet effectiveness to mitigate head, serious head, face, neck and fatal head injury in a crash or fall. Methods: Four electronic databases (MEDLINE, EMBASE, COMPENDEX and SCOPUS) were searched for relevant, peer-reviewed articles in English. Included studies reported medically diagnosed head, face and neck injuries where helmet use was known. Nonapproved helmets were excluded where possible. Summary odds ratios (OR) were obtained using multivariate meta-regression models stratified by injury type and severity. Time trends and publication bias were assessed. Results: A total of 43 studies met inclusion criteria and 40 studies were included in the meta-analysis with data from over 64 000 injured cyclists. For cyclists involved in a crash or fall, helmet use was associated with odds reductions for head (OR=0.49, 95% confidence interval (CI): 0.42-0.57), serious head (OR=0.31, 95% CI: 0.25-0.37), face (OR=0.67, 95% CI: 0.56-0.81) and fatal head injury (OR==0.35, 95% CI: 0.14-0.88). No clear evidence of an association between helmet use and neck injury was found (OR=0.96, 95% CI: 0.74-1.25). There was no evidence of time trends or publication bias. Conclusions: Bicycle helmet use was associated with reduced odds of head injury, serious head injury, facial injury and fatal head injury. The reduction was greater for serious or fatal head injury. Neck injury was rare and not associated with helmet use. These results support the use of strategies to increase the uptake of bicycle helmets as part of a comprehensive cycling safety plan. © The Author 2016; all rights reserved.