Despite popular opinion to the contrary, early scientific evidence pointed to a lack of support for the view that people's actions are guided by their attitudes. One response to the lack of correspondence between attitudes and behaviour has been to consider the role of other factors. One factor that has received attention is norms – the unwritten and often unspoken rules for how we should behave. We present an overview of the social identity approach to attitude–behaviour relations, which argues that norms play a significant role in the attitude–behaviour relationship if and only if the norms come from salient and important reference groups. We will then discuss a program of research that supports this analysis and examines the motivations that underpin group-mediated attitude–behaviour consistency. Finally, we will discuss research that investigates the distinction between descriptive group norms (what group members do) and injunctive group norms (what group members approve of). We focus on how the interactions between these types of norms can inform behaviour change campaigns.