We discuss the idea that competition-based motives boost low-status group members’ support for group-based hierarchy and inequality. Specifically, the more low-status group members feel motivated to compete with a relevant high-status outgroup, based on the belief that existing status positions may be reversed, the more they will defend status differentials (i.e., high social dominance orientation; SDO). Using minimal groups (N = 113), we manipulated ingroup (low vs. high) status, and primed unstable status positions to all participants. As expected, we found that SDO positively mediates the relation between ingroup identification and collective action, when ingroup’s status is perceived to be low and status positions are perceived as highly unstable. We discuss the implications of considering situational and contextual factors to better understand individuals’ support for group-based hierarchies and inequality, and the advantages of considering ideological processes in predicting collective action.