Objective: To gain insight into the food availability, the perceived food environment, and social norm perceptions in favour of healthy and vegetarian food consumption at a festival. Design: Two cross-sectional substudies were conducted to audit food and beverages at the festival, and to measure visitors' perceptions of the festival food environment (accessibility, affordability, availability, diversity, quality) and their social norms perceptions via a mobile survey. Setting: Public music festival, the Netherlands. Sample: 75 food stands and 153 adult festival visitors. Results: 75 food stands offered 627 food and beverage items, of which 92.4% were not supportive of a healthy diet. Of all food items, 46.6% were vegetarian (including 20% fries). Participants especially perceived the festival food environment as unsupportive of healthy choices. They also had weak descriptive and injunctive social norm perceptions in favour of healthy and vegetarian food consumption. However, they had stronger descriptive (t(152)=-5.5; p<0.001) and injunctive norm perceptions (t(152)=-4.5; p<0.001) of vegetarian food consumption (mean descriptive social norm perception=2.42; SD=0.82; mean injunctive social norm perception=3.14; SD=0.78), than healthy food consumption (mean descriptive social norm perception=2.10; SD=0.76; mean injunctive social norm perception=2.93; SD=0.78). Participants had stronger injunctive than descriptive social norm perceptions of healthy (t(152)=-12.4; p<0.001) and vegetarian (t(152)=-11.3; p<0.001) food consumption. Participants' perceived food environment and their perception of social norms were positively correlated. Conclusion: The festival's food environment appears unsupportive of healthy and vegetarian food consumption. The limited availability of healthy and vegetarian food coincided with weak social norm perceptions encouraging their consumption, particularly descriptive norms that arise from observing others. The food environment may stand in the way of developing descriptive norms ...