Social norms-based interventions offer a promising avenue to encourage proenvironmental behavior change. From a social identity perspective, it is argued that social norms communications will be maximally effective when they are tied to salient group memberships and supportive ingroup norms are communicated. Across four studies conducted in a water scarce region in England we demonstrate that a water conservation ingroup norms appeal encourages a shift in behavioral intentions and behavior. We provide initial evidence of the efficacy of the appeal against an information-only message (Study 1) and the mediating role of perceived ingroup norms (Study 2). Across two randomized control field trials, we find the appeal is more effective than a general social norms appeal (Study 3) and that sign-ups to a water-savings program significantly increase when the appeal is integrated into existing promotional materials (Study 4). We conclude by discussing how these insights can offer new perspectives on proenvironmental behavior change.