Objectives: The objectives of the present study were to describe the injury profiles of cyclists presenting to an ED and determine the risk of significant head injury associated with bicycle helmet use. Methods: This was a retrospective single trauma centre study of all adult cyclists presenting to an inner city ED and undergoing a trauma team review between January 2012 and June 2014. The outcome of interest was significant head injury defined as any head injury with an Abbreviated Injury Scale score of two or more. Variables analysed included demographic characteristics, helmet use at time of incident, location, time and the presence of intoxication. Results: The most common body regions were upper limb injuries (57%), followed by head injuries (43%), facial injuries (30%) and lower limb injuries (24%). A lower proportion of people wearing helmets had significant head injury (17% vs 31%, P = 0.018) or facial injury (26% vs 48%, P = 0.0017) compared with non-helmet users. After adjustment for important covariates, helmet use was associated with a 70% decrease in the odds of significant head injury (odds ratio 0.34, 95% confidence interval 0.15, 0.76, P = 0.008). Conclusions: Head injuries were common after inner city cycling incidents. The use of helmets was associated with a reduction in significant head injury.