Gender differences in concern about climate change are highly correlated with economic development: when countries are wealthier, a gap emerges whereby women are more likely than men to express concern about our changing climate. These differences stem from cross-national variation in men’s attitudes. Men, more than women, tend to be less concerned about climate change when countries are wealthier. This article develops a new theory about the perceived costs and benefits of climate mitigation policy to explain this pattern. At the country level, the perceived benefits of mitigation tend to decrease with economic development, whereas the perceived costs increase. At the individual level, the perceived costs of mitigation tend to increase with economic development for men more than for women. Evidence from existing surveys from every world region, an original 10-country survey in the Americas and Europe, and focus groups in Peru and the United States support the theory.