The aim of this paper is to examine how framing influences people’ s cooperation behavior in social dilemmas. In Experiment 1 we investigated the influence of outcome valence (positive vs. negative outcome) and externality valence (positive vs. negative externality) framing on players’ willingness to cooperate in a repeated public good game. We found a significant interaction effect on first-round cooperation, indicating larger cooperation rates when there is a negative outcome valence and a positive externality on others. Furthermore, this effect remained largely stable when comparing cooperation over all rounds, resulting in 45–63% increased cooperation compared to the other conditions. In Experiment 2 we replicated the effect in an applied vignette study, lending support for the generalizability of this framing effect. Taken together, these findings suggest that public goods provisions may be increased substantially by framing the situation’s outcome valence as negative rather than positive.