Recent evidence points to the idea that dog aggression is highly variable at the individual level and affected by various factors, such as the owner’s personality or dog-owner interactions. Additionally, studies on dog aggression show limited differences between dog breeds, or differences that are unrelated to the legislative status of those breeds, even though breed-specific legislation prohibits the ownership of so-called “dangerous” breeds. Here, I examined differences in aggression among breed groups in the Swedish dog population, using a combination of personality questionnaires and video analysis of dog-human play. Aggressive behaviour of dogs was assessed using the short version of the Canine Behavioural Assessment and Research Questionnaire, their owners’ personality was measured with the Big Five Inventory, and the play interactions were recorded by the participants at their homes. The results showed no significant differences in aggression based on the legislative status, and no single breed group could be identified as having significantly higher or lower aggression scores. More neurotic owners had more aggressive dogs, while the owners’ agreeableness and the dog’s engagement in keep-away play were both negatively associated with dog aggression. The results suggest that dog aggression is affected by a complex interplay between many variables, rather than being solely based on breed, thus providing further reason to question the existence of a scientific basis for breed specific legislation.