There are well documented acute and chronic effects of cannabis use. However, less is known about any effects on safety within the context of work and everyday life. The aim of the study was to examine any association between cannabis use and injuries and accidents. A postal questionnaire survey was conducted among people selected at random from the electoral registers of Cardiff and Merthyr Tydfil. Cannabis use was associated with both minor injuries and accidents, particularly among those with high levels of other associated risk factors. Cannabis use was associated with a significant detrimental impact on safety. It is possible that this is linked to an amplification of other risk factors associated with accidents and injuries. This has potentially wide reaching implications particularly in the context of other work and lifestyle characteristics.