Prior studies on population health have reported an "immigrant health advantage" in which immigrants tend to show better health outcomes compared to their native-born racial/ethnic counterparts. Migrant selectivity and cultural buffering have been proposed as explanations for this relative advantage, predominantly in studies that focus on Latino immigrants' health in the US. This study adds to the relatively scant literature on black immigrant health advantage by comparing the two hypotheses (migrant selectivity and cultural buffering) as related to black immigrant health. The effect of nativity on infant low birth weight is tested using data from the US Fragile Families and Child Wellbeing Study. Results indicate that immigrant black mothers do have relatively better health outcomes that may result from cultural buffering, which reduces their risky health behaviors.