COVID-19 is an unprecedented threat and an effective response requires a collective effort: engagement in preventive health behaviors, even from people at low risk. Previous research demonstrates that belongingness to social groups can promote prosocial, preventive health behaviors. The current research tests the effects of belongingness to two types of groups, intimate (family) and social category (nation), on intentions to comply with preventive health behaviors and reasons for these behaviors. We conducted three studies using French participants at low risk of grave effects from COVID-19 (total N = 875). In Study 1, across three time periods, belongingness was correlated with greater intentions to comply with preventive behaviors when these behaviors were not enforced by law. In Study 2, we experimentally manipulated threat to belongingness (vs. no threat). When belongingness was threatened, participants were less concerned with protecting vulnerable people. Closeness to family predicted preventive behavior intentions and both self-centered and prosocial reasons for these behaviors, regardless of condition. National identification buffered the negative effects of the threat to belongingness condition on preventive behavior intentions. In Study 3, we experimentally primed thoughts of belongingness to family vs. nation vs. control condition. We found greater intentions to engage in preventive behaviors and greater concern with protecting oneself and close relatives in the family condition. In summary, belongingness to one's family promotes preventive behavior intentions and the reasons given are to protect both oneself and others. Self-reported (but not primed) national identification can be related to prevention behavior intentions under certain conditions.