Several studies provide evidence of group-centric policy attitudes, that is, citizens evaluating policies based on linkages with visible social groups. The existing literature generally points to the role of media imagery, rhetoric and prominent political sponsors in driving group-centric attitudes. This article theorizes and tests an alternative source: exposure to rising local ethnic diversity. Focusing on the issue of crime, it first develops a theoretical account of how casual observation in the local context can give rise to ethnic stereotypes. Then, using two large, nationally representative datasets on citizen group and policy attitudes linked with registry data on local ethnic diversity, each spanning 20 years, it shows that crime attitudes become more strongly linked with immigration attitudes as local ethnic diversity rises. The results suggest that the typically emphasized ‘top-down’ influence on group-centric attitudes by elite actors is complemented by ‘bottom-up’ local processes of experiential learning about group–policy linkages.