In this research we explore the relationship between social heterogeneity and volunteering across U.S. metropolitan areas testing a theory that race heterogeneity, racial segregation, and income inequality are negatively associated with the rate of volunteering. Theorizing that social heterogeneity will have different effects for religious and secular volunteering rates, we analyze them separately. We use nonlinear multilevel models to analyze nearly 200,000 individuals across 248 cities, controlling for nonprofits per capita, religious congregations per capita, proportion of the population with college degrees, and the family poverty rate. While much of the intercity variation in volunteering is due to the composition of the population living in each city, we find general support for the predicted negative effect of social heterogeneity on volunteering. However, the effects vary by volunteering type. Race heterogeneity is negatively related only to secular volunteering, racial segregation is negatively related to both general volunteering and secular volunteering, and income inequality is negatively related to all types of volunteering.