Transracial adoptees represent a specific group of immigrants who experience unique immigration processes that bring them face-to-face with two cultural backgrounds: that of their heritage culture on one hand and that of their national culture on the other hand. However, there is a scarcity of studies focused on the way these processes unfold within adoptive families. This study was aimed at exploring how transracial adoptees cope with the construction of their ethnic identity. Administering a self-report questionnaire to 127 transracial adoptees and their mothers, for a total of 254 participants, we first investigated the association between mothers' cultural socialisation (enculturation and preparation for bias strategies) and adoptees' ethnic identity (i.e. ethnic identity exploration and ethnic identity affirmation dimensions). We then investigated whether ethnic identity affects self-esteem by testing the hypothesis that national identity moderates the relationship between ethnic identity and self-esteem. Results revealed that mothers' enculturation (but not their preparation for bias) supported adoptees' ethnic identity exploration, which in turn was positively associated with ethnic identity affirmation. Moreover, we confirmed the moderation effect: ethnic identity affirmation enhanced the level of self-esteem, but only for those adoptees who perceived a higher degree of national identity affirmation.