Social norm interventions represent a low-cost and effective policy tool that havebeen shown to generate behaviour change in a number of contexts. We investigatewhether valence framing impacts the effectiveness of a social norm intervention onprosocial behaviour. We use Amazon Mechanical Turk in conjunction with oTreeto conduct an experiment in which we manipulate descriptive beliefs and originalendowments in the context of a dictator game. We find that the impact of a socialnorm intervention appears to be significantly greater in a frame of negative valencevs. a frame of positive valence. Loss aversion and positional preferences could playa role in these findings. Regression results furthermore indicate a differences in thedeterminants of allocation decisions across frames, suggesting that normative beliefsmatter more in a positive frame, whereas descriptive beliefs matter more in a negativeframe. This work contributes to a better understanding of framing effects as well asthe conditions under which normative considerations are most salient. On a practicallevel, it points to an opportunity for policymakers to substantially improve upon thedesign of social norm interventions