Disparities in poverty and health care access barriers have a negative impact on the health and wellness of population subsets that bear a disproportionate share of these socioeconomic disadvantages, such as African Americans and Hispanic/Latina Americans. The more advanced stage distribution of breast cancer in these two population subsets is likely related to imbalance in distribution of socioeconomic resources in the United States. However, differences in the breast cancer burden of population subsets defined by racial/ethnic identity are also influenced by race/ethnicity-associated variation in tumor biology and hereditary susceptibility. Compared with white Americans, African-American women have higher population-based breast cancer mortality rates, which are at least partly explained by an increased risk for the biologically aggressive triple-negative phenotype. International studies correlate West African ancestry with predisposition for triple-negative breast cancer. In contrast, Hispanic/Latina Americans have lower population-based incidence and mortality rates for breast cancer despite their increased rates of socioeconomic challenges. Genetic studies suggest that extent of Native American ancestry among Hispanic/Latina women may reduce breast cancer risk. Eradication of disparate access to breast cancer early detection and treatment strategies is a public health imperative, but research to elucidate the genetics of breast cancer related to racial/ethnic identity is equally important as we strive to comprehensively define this complex disease.