The protective effect of family structure and socioeconomic status (SES) on physical and mental health is well established. There are reports, however, documenting a smaller return of SES among Blacks compared to Whites, also known as Blacks' diminished return. Using a national sample, this study investigated race by gender differences in the effects of family structure and family SES on subsequent body mass index (BMI) over a 15-year period. This 15-year longitudinal study used data from the Fragile Families and Child Wellbeing Study (FFCWS), in-home survey. This study followed 1781 youth from birth to age 15. The sample was composed of White males (n = 241, 13.5%), White females (n = 224, 12.6%), Black males (n = 667, 37.5%), and Black females (n = 649, 36.4%). Family structure and family SES (maternal education and income to need ratio) at birth were the independent variables. BMI at age 15 was the outcome. Race and gender were the moderators. Linear regression models were run in the pooled sample, in addition to race by gender groups. In the pooled sample, married parents, more maternal education, and income to need ratio were all protective against high BMI of youth at 15 years of age. Race interacted with family structure, maternal education, and income to need ratio on BMI, indicating smaller effects for Blacks compared to Whites. Gender did not interact with SES indicators on BMI. Race by gender stratified regressions showed the most consistent associations between family SES and future BMI for White females followed by White males. Family structure, maternal education, and income to need ratio were not associated with lower BMI in Black males or females. The health gain received from family economic resources over time is smaller for male and female Black youth than for male and female White youth. Equalizing access to economic resources may not be enough to eliminate health disparities in obesity. Policies should address qualitative differences in the lives of Whites and Blacks which result in diminished health returns with similar SES resources. Policies should address structural and societal barriers that hold Blacks against translation of their SES resources to health outcomes.