Abstract Introduction The Caribbean accounts for half of all foreign-born blacks in the USA. The biggest contributors to this immigrant population come from Cuba, Dominican Republic (DR), Jamaica, Haiti and Trinidad and Tobago. Breast cancer (BC) is the most commonly diagnosed cancer in US Black women and the second cancer related cause of death. Breast cancer in the most common cause of death of native Caribbean women. In our previous work, we found that Caribbean immigrants with breast had a better overall survival than US born Blacks. The primary objective of this study was to investigate the etiology and outcomes within the most populace Caribbean born immigrants compared to US born Black women within our cohort. Methods Data were obtained from Jackson Memorial Health Systems and University of Miami Health System Tumor Registry. Data from 1,082 Black patients were used to estimate hazard rations (HRs) of women born in Haiti, Jamaica, Bahamas, Cuba, Dominican Republic or the US born (USB) using Cox proportional hazards regression analysis for overall survival. Clinicopathologic and treatment characteristics of women from each island were compared to USB using Chi Squared testing and independent sample t-test. Results The sub-cohort contained data from Haitian (250), Jamaican (89), Bahamian (43), Dominican (38), Cuban (38) and 624 USB women. Compared to USB (57.6 years), of all the sub-groups the Bahamians were the youngest (50.5 years, P <0.001) and presented at the highest advanced stage in the cohort (54.3% vs USB 35.3%; P=0.02). Cubans (26.5%), Jamaicans (26.2%), and Haitians (25.8%) had a higher prevalence of HER2+ breast cancer in contrast to USB (17.7%), Bahamians (18.9%) and Dominicans (18.9%). Surgery was a favorable factor for survival in USB (aHR=0.26 (0.19-0.36), p<0.001), Bahamians (aHR=0.05 (0.01-0.47), p=0.008) and Jamaicans (aHR=0.08 (0.03-0.24), p<0.001). Haitian were the only immigrant group with a significant favorable outcome from radiation therapy (aHR=0.45, 95% 0.27-0.77; P=0.004). Cubans and Dominicans had a significant favorable response to surgery (aHR=0.25 (0.04-1.58), p=0.14) and radiation (aHR=0.48 (0.05-4.19), p=0.51) but did not reach statistical significance due to small sample size. Conclusion This data demonstrates and highlights intra-island and ethnic differences linked to clinicopathologic features of breast cancer in Black women living in the US. Further studies are needed to identify biological factors impacting the etiology and outcomes breast cancer in the immigrant Caribbean population and US born Black. Citation Format: Danielle A Cerbon, Matthew Schlumbrecht, Camille Ragin, Priscila Barreto-Coelho, Judith Hurley, Sophia HL George. Intra-Caribbean Island differences drive breast cancer outcomes in US Caribbean-immigrant women compared to US-born Black women [abstract]. In: Proceedings of the Twelfth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2019 Sep 20-23; San Francisco, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl_2):Abstract nr B098.