Sustainable habits and lifestyles are widely regarded as coming at a cost to a person’s comfort and convenience, as requiring sacrifices to individual well-being. This randomized controlled trial found, to the contrary, that pro-environmental behavior increases individuals’ happiness and well-being. The magnitude of this effect was equivalent to that of behaviors chosen specifically to be enjoyable and fulfilling, did not vary with individuals’ environmental attitudes, typical level of pro-environmental behavior, or political orientation. There was also evidence of a positive dose-response relationship, indicating that more pro-environmental behavior leads to greater increases in well-being. Though they contradict popular perceptions, these findings are consistent with prominent theories of human motivation and well-being and prior, correlational research on pro-environmental behavior and well-being.