The present study examined whether self-esteem mediates the relationship between two aspects of ethnic identity (i.e. ethnic identity exploration and ethnic identity commitment-affirmation) and externalizing problem behaviour in Dutch, Turkish-Dutch and Moroccan-Dutch adolescents living in the Netherlands. A total number of 345 adolescents (115 Dutch, 115 Turkish-Dutch, 115 Moroccan-Dutch) with a mean age of 14.5 filled in questionnaires at school. Turkish-Dutch and Moroccan-Dutch adolescents reported higher levels of both aspects of ethnic identity than their native Dutch counterparts, but there were no ethnic differences in self-esteem and externalizing problem behaviour. Only in the Moroccan-Dutch group was support found for the mediational model: stronger ethnic identity commitment-affirmation was related to a higher level of self-esteem, which, in turn, was related to a lower level of externalizing problem behaviour.