While environmental motivation is an acknowledged predictor of sustainable behavior, its relation to individuals’ greenhouse gas emissions seems much weaker. We argue that one explanation for this seeming paradox is that (I) sustainable choices do not necessarily entail substantially lower emissions, and (II) individuals might not always act upon, or (III) correctly judge, emission differences between sustainable and non-sustainable behaviors. Data on the cafeteria meal choices and related emissions of N = 115 students were collected through on-site and online recruitment. A series of regression models revealed that environmental motivation was strongly related to sustainable (vegan or vegetarian) meal choices. Emission differences between available sustainable and non-sustainable (omnivorous) meals and food-related emission knowledge did not affect participants’ choices. Yet, emission differences between available sustainable and non-sustainable options strongly moderated the effect of environmental motivation on emissions. Essentially, while environmental motivation seems to consistently predict sustainable meal choices, environmental motivation’s emission-reduction potential is context-dependent. This implies that relating motivation with emissions needs to account for the context to provide a fair assessment of the emission-effect of environmental motivation.