In this study, we aimed to understand how restaurants can contribute to climate change mitigation via menu design. We investigated two types of interventions: changing the configuration of menu entries with variable side dishes so that the most climate-friendly option is set as the default and indicating the greenhouse gas emission of each dish via carbon labels. In an online simulation experiment, 265 participants were shown the menus of nine different restaurants and had to choose exactly one dish per menu. In six menus, the main dishes were presented with different default options: the side dish was associated either with the highest or with the lowest greenhouse gas emissions. The other three menus consisted of unitary dishes for which the default rules did not apply. All menus were presented either with or without carbon labels for each dish option. The results indicated that more climate-friendly dish choices resulting in lower greenhouse gas emissions were made with the low-emission than the high-emission default condition, and when carbon labels were present rather than absent. The effects of both interventions interacted, which indicates that the interventions partly overlap with regard to cognitive predecessors of choice behavior, such as attentional focus and social norms. The results suggest that the design of restaurant menus has a considerable effect on the carbon footprint of dining.