A large theoretical and empirical literature documents the central role of familismo (i.e., a strong emphasis on family) in the functioning of Latino youth. Few studies, however, have examined its association with early childhood functioning. The present study explored the potential risk and protective effects of maternal familismo on the adaptive and mental health functioning of 4 - 5 year old Latino children. A sample of 205 Mexican and 147 Dominican immigrant families was recruited from New York City. Mothers reported on their level of familismo, and acculturative status. Mothers and teachers rated child adaptive behavior and internalizing and externalizing problems. Findings suggest that maternal familismo is not uniformly associated with positive or negative early developmental outcomes but that its effects are moderated by child gender, family poverty and cultural (e.g., maternal ethnic and US American identity) characteristics. In addition, different mechanisms were identified for each ethnic group. Familismo was associated both positively (for boys) and negatively (for poor children) with adaptive behavior in the Mexican American sample. In the Dominican American sample, familismo showed a wide range of positive, albeit moderated, effects. Prevention efforts that help parents critically evaluate the impact of familismo on family processes, and preserve those manifestations of familismo that are protective, may best promote Latino child well-being.