We examined the current literature to understand factors that influence endocrine therapy (ET) adherence among racial/ethnic and socioeconomic subpopulations of breast cancer patients. We searched PubMed and PsycINFO databases for studies from January 1, 1978, to June 20, 2014, and January 1, 1991, to June 20, 2014, respectively, and hand-searched articles from relevant literature reviews. We abstracted and synthesized results within a social ecological framework. Fourteen articles met all inclusion criteria. The majority of included articles reported significant underuse of ET among minority and low-income women. Modifiable intrapersonal, interpersonal, and community-level factors are associated with ET use, and these factors vary across subgroups. Both race/ethnicity and socioeconomic status are associated with ET use in most settings. Variation in factors associated with ET use across subgroups indicates the need for more nuanced research and targeted interventions among breast cancer patients.