We show that two simple and nonintrusive ‘nudges’ – reducing plate size and providing social cues – reduce the amount of food waste in hotel restaurants by around 20%. The results are statistically significant. They are also environmentally substantial as food waste is a major contributor to climate change and other forms of environmental degradation. Given the magnitude of the contribution of food waste to global environmental change, it is surprising that this issue has not received greater attention. The measures reduce the amount of food the restaurants need to purchase, and there is no change in guest satisfaction, making it likely that profits will increase. The measures thus constitute potential win–win opportunities.