Objective To examine whether hospitals where patients obtain care explain racial/ethnic differences in treatment delay. Data Source Surveillance, Epidemiology, and End Results data linked with Medicare claims. Study Design We examined delays in adjuvant chemotherapy or radiation for women diagnosed with stage I–III breast cancer during 1992–2007. We used multivariable logistic regression to assess the probability of delay by race/ethnicity and included hospital fixed effects to assess whether hospitals explained disparities. Principal Findings Among 54,592 women, black (11.9 percent) and Hispanic (9.9 percent) women had more delays than whites (7.8 percent, p < .0001). After adjustment, black (vs. white) women had higher odds of delay (odds ratio = 1.25, 95 percent confidence interval = 1.10–1.42), attenuated somewhat by including hospital fixed effects (OR = 1.17, 95 percent CI = 1.02–1.33). Conclusions Hospitals are the important contributors to racial disparities in treatment delay.