This research explores the interplay between income inequality and sustainable consumption, highlighting how socioeconomic disparities shape consumer behavior. Using secondary data from 20 countries, a vignette experiment, and UK survey data, we find that both objective and perceived high levels of income inequality reduce sustainable consumption. Drawing on norm activation theory, we show that rising inequality diminishes consumers’ sense of responsibility for environmental outcomes and reduces their awareness of the environmental impact of their consumption choices. Our findings emphasize the interconnected nature of social and environmental dimensions of sustainable development. Reducing income inequality emerges as a pathway to foster sustainable consumption, suggesting that redistributive policies may not only promote equity but also enhance environmental outcomes. We also discuss how businesses and policymakers can mitigate the negative effects of inequality on sustainable consumption by promoting low-cost sustainability practices, leveraging impact labeling, and empowering consumers in regions with high inequality.