Inequalities in health behaviours (i.e., the tendency of socially disadvantaged people, compared to more advantaged people, to engage in fewer healthy behaviours) have been mostly accounted for by individual and environmental factors. The present research proposed to consider a social identity perspective by examining the combined impact of class-related norms and social class identification on intentions to engage in healthy behaviours. Based on a correlational study (N = 407), our results showed that healthy behaviours were perceived to be more normative of the upper-middle class than the lower-middle class, regardless of participants' class membership. We also found that intentions to perform healthy behaviours increased among those who highly identified with the upper-middle class, when they perceived healthy behaviours as highly normative of that class. Moreover, those who highly identified with the lower-middle class (vs. the upper-middle class) reported lower intentions when healthy behaviours were viewed as normative of the upper-middle class. This suggests that a stronger prevalence of healthy behaviours among socially privileged people is driven by in-group conformity, whereas the tendency to act less healthily among those disadvantaged would be underpinned by out-group rejection. More generally, these findings underscore the importance of social identity factors in providing novel insights for research on health disparities.Inequalities in health behaviours (i.e., the tendency of socially disadvantaged people, compared to more advantaged people, to engage in fewer healthy behaviours) have been mostly accounted for by individual and environmental factors. The present research proposed to consider a social identity perspective by examining the combined impact of class-related norms and social class identification on intentions to engage in healthy behaviours. Based on a correlational study (N = 407), our results showed that healthy behaviours were perceived to be more normative of the upper-middle class than the lower-middle class, regardless of participants' class membership. We also found that intentions to perform healthy behaviours increased among those who highly identified with the upper-middle class, when they perceived healthy behaviours as highly normative of that class. Moreover, those who highly identified with the lower-middle class (vs. the upper-middle class) reported lower intentions when healthy behaviours were viewed as normative of the upper-middle class. This suggests that a stronger prevalence of healthy behaviours among socially privileged people is driven by in-group conformity, whereas the tendency to act less healthily among those disadvantaged would be underpinned by out-group rejection. More generally, these findings underscore the importance of social identity factors in providing novel insights for research on health disparities.