Music festivals are often high-risk settings associated with large numbers of visitors and high alcohol intoxication levels, which contribute to a number of public health-related problems. According to the Swedish Alcohol Act, servers are responsible for not overserving alcohol to obviously intoxicated patrons. The aim of the current study was to examine compliance to the Swedish Alcohol Act at music festivals by assessing the rate of alcohol overserving to festival-goers. We conducted a study at a large music festival in Sweden hosting approximately 50,000 visitors. Professional actors, i.e., pseudo-patrons, enacted a standardized scene in which a highly intoxicated festival-goer attempted to buy beer at licensed premises inside the festival. Observers monitored each attempt. A total of 52 purchase attempts were conducted. The rate of overserving was 26.9% and was not influenced by the server’s gender, the number of servers, or the level of crowdedness at the bar area. Overserving differed between server age groups, which was not statistically significant when controlling for other factors. Compliance to the Alcohol Act at the festival can be improved. Intoxication levels and related problems can be reduced by implementing a multicomponent intervention including staff training, policy work, and improved enforcement.