While public concern about climate change is growing, individuals often face information frictions and psychological barriers to pro-environmental behaviour. In this study, we design and test an edutainment intervention that aims at promoting more sustainable food consumption through a serious video game. Different game versions either link player actions to visual impacts on the in-game environment or to social feedback through interactions with non-player characters, or both. To evaluate the effects on real-life attitudes, knowledge, and behaviour, we conduct an online survey experiment (n = 4,034 UK adults) that embeds an incentivised grocery shopping task. Compared to subjects who played a control version without educational content, treated subjects purchase food products that are around 20% more environmentally sustainable immediately after playing the game. In a follow-up survey several weeks later, effects are still strongly significant at around 8-10%. These behavioural changes are driven both by improved knowledge about environmental impacts of food as well as an increase in pro-environmental attitudes. Effects are particularly persistent among individuals with lower baseline environmental attitudes.