Background: Determinants of variation in therapy utilization and OS are unclear for patients diagnosed with hormone receptor+, human epidermal growth factor 2 positive (HER2+) MBC. This study aimed to identify if there are disparities in first-line treatment patterns and outcomes for this subpopulation of MBC patients. Methods: We analyzed MBC patients included in the National Cancer Database diagnosed with estrogen receptor-positive (ER+) and/or progesterone receptor-positive (PR+) and HER2+ disease (i.e. triple positive) treated with endocrine therapy or chemotherapy between 2010 and 2015. Analyses describe the distribution of treatments administered in the first-line setting. Kaplan-Meier method was used to estimate distributions of OS, which were compared among patient cohorts using the log-rank test. Results: Of the 6215 patients diagnosed with triple positive MBC, the majority were 50-70 years old (n=3414 [55%]), female (n= 6122 [98%]), and white (n=4478 [72%]). Four distinct treatment patters were identified; hormonal therapy was the most common (n= 2289 [37%]), followed by hormonal therapy + anit-HER2 (n=1471 [24%]), chemotherapy (1280 [20%]), and chemotherapy + anit-HER2 (n=1175 (19%)). Significant differences in demographic, socioeconomic, and disease characteristics were identified across groups. Disparities in OS were also observed; the unadjusted 5-year OS was substantially lower among older patients, African Americans (AA), those with government insurance, and lower income (Table). Conclusions: This is the first study to report disparities in treatment patterns and OS among real-world triple positive MBC patients. Further investigation is required to determine if there are independent causal associations between poor prognosis and the identified demographic and socioeconomic characteristics.