Background: There is evidence that race/ethnicity and comorbidities are negatively associated with outcomes in female patients with Breast Cancer (BC). However, this interaction is not well understood. The objective of this review is to identify whether Comorbidity Indices (CIs) can be used to predict outcomes by race/ ethnicity in patients with BC. Methods: A systematic literature review on the use of CIs to predict outcomes by race in patients with BC was performed on English-language articles published 1987-2020 using Ovid. Two independent researchers performed two levels of article selection following PRISMA, and risk of bias (using the Newcastle-Ottawa Scale) was assessed. Results: Ten studies were identified, all of which used the Charlson CI (CCI) or CCI derivative. All studies were conducted in North America. Most evaluated White/non-Hispanic White (n = 9) or Black/African American (AA) (n = 8) patients; fewer evaluated Asian/Pacific Islander, Hispanic, American Indian/Alaska Native, or First Nations patients. Overall, the results were mixed. Some studies that stratified outcomes by race found that only certain disease stages, outcomes, racial/ethnic subgroups, or higher CCI scores were associated with higher risk of mortality, while others did not. One study found that CCI scores were not associated with survival when added to models using race to predict outcomes, while others found a significant association. Conclusion: There is limited research on the interaction between race, comorbidities, and outcomes in BC. The studies in this review showed mixed results for the predictive capability of the CCI in racial/ethnic minorities.