Abstract Introduction: Black women are more likely to experience delays in receipt of breast cancer surgery and adjuvant hormone treatment (AHT) compared to White women. The aim of this study was to assess the effect modifiers that influence the relationship between race and delay in receipt of surgery and AHT among patients diagnosed with breast cancer. Methods: Breast cancer cases were obtained retrospectively from the SC Central Cancer Registry, linked with administrative data from the State Health Plan and Medicaid Plan from 2002 to 2010. The main outcome variables were diagnosis-to-surgery time and diagnosis-to-AHT for breast cancer. The main exposure variable was patient race (White vs Black). Chi-square tests, logistic regression and generalized linear regression analyses were conducted to compare patients' treatment delays among Blacks and Whites to identify effect modifiers in the receipt of delayed treatment. Receipt of surgery was dichotomized into early and late receipt of treatment using the median of 22 days as cut-off. In assessing the relationship between race and time to surgery, the identified effect modifiers were marital status, urban status, and distance to provider of first service. The multivariable logistic model was stratified by the effect modifier variables and each model was adjusted for age, year of diagnosis, hormone-receptor status, stage, grade, and enrolment in Best Chance Network (BCN) program. Results: A total of 2,155 breast cancer patients (nWhites=1557; nBlacks= 598) were reported in the study period. Multivariable logistic regression that adjusted for 8 variables (age, year of diagnosis, hormone receptor status, cancer stage, cancer grade, being in BCN, definitive surgery type and insurance provider) showed that the odds of late receipt of surgery was 1.96 (95% CI: 1.38-2.79) among unmarried Black women compared with unmarried White women and 1.40 (95% CI: 1.08-1.82) among Blacks who live in urban areas compared with White women who lived in urban areas. Result of multivariable generalized linear regression analysis showed that among Blacks who had surgery >30 days after diagnosis, the least square means from diagnosis to AHT were statistically increased by 42 days compared to Whites, while among Blacks who had surgery >60 days after diagnosis, the least square means from diagnosis to AHT were statistically increased by 63 days compared to Whites. Conclusions: Late receipt of surgery was higher among Blacks who were unmarried and lived in rural areas. Those who received late surgery also had a higher likelihood of receiving late AHT. To improve timely receipt of surgery, efforts need to be directed at Black breast cancer patients who are not married and who live in rural areas. Navigation efforts directed at reducing delays in receipt of surgery should also be directed at reducing delays in receipt of AHT. Citation Format: Oluwole A. Babatunde, Swann A. Adams, Jan M. Eberth, Tisha M. Felder, Robert Moran, Samantha N. Truman, Christian Alvarado, James R. Hebert. Effect modifiers of surgery and adjuvant hormone treatment delays among patients diagnosed with breast cancer in South Carolina [abstract]. In: Proceedings of the Eleventh AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2018 Nov 2-5; New Orleans, LA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2020;29(6 Suppl):Abstract nr B075.