The RAC1 GTPase can promote elongated cell morphology during cell migration. Here, Oberoi et al. find that the inhibitor of apoptosis (IAP) proteins can directly target RAC1 for proteasomal degradation and that their loss results in increased RAC1 levels, cell elongation and enhanced directed migration. Consistent with an interaction previously observed between RAC1 and a Drosophila melanogaster IAP, they show here that both X chromosome-linked IAP (XIAP) and cellular IAP1 (cIAP1) act directly as E3 ligases for RAC1. This control mechanism appears to be physiologically relevant during development of the zebrafish hindbrain.