The aim of the current study was to quantify the risk of tail injury, to evaluate the extent to which tail docking reduces this risk, and to identify other major risk factors for tail injury in dogs in Great Britain. A nested case-control study was conducted during 2008 and 2009. Data were obtained from a stratified random sample of veterinary practices throughout Great Britain, and questionnaires were sent to owners of dogs with tail injuries and owners of a randomly selected sample of dogs without tail injuries. The risks of injury were reported adjusting for the sampling approach, and mixed effects logistic regression was used to develop a multivariable model for risk factors associated with tail injury. Two hundred and eighty-one tail injuries were recorded from a population of 138,212 dogs attending 52 participating practices. The weighted risk of tail injuries was 0.23 per cent (95 per cent confidence interval 0.20 to 0.25 per cent). Thirty-six per cent of injuries were reportedly related to injuries sustained in the home, 17.5 per cent were outdoor-related injuries, 14.4 per cent were due to the tail being caught in a door, for 16.5 per cent the cause was unknown and the remainder were due to other causes. Dogs with a wide angle of wag and dogs kept in kennels were at significantly higher risk of sustaining a tail injury. Dogs with docked tails were significantly less likely to sustain a tail injury; however, approximately 500 dogs would need to be docked in order to prevent one tail injury. English springer spaniels, cocker spaniels, greyhounds, lurchers and whippets were all at significantly higher risk when compared to labradors and other retrievers. Differences between countries (England, Scotland and Wales) and between rural and urban environments were not significant.