BACKGROUND: The objective of this study is to understand the effect of Medicaid expansion under the Affordable Care Act (ACA) on patterns of surgical care among low-income breast cancer patients. Emerging literature suggests cancer patients in Medicaid expansion states are presenting with earlier stages of disease. However, less is known regarding the implications of Medicaid expansion on patterns of surgical care in low-income women. PATIENTS AND METHODS: We compared nonmetastatic 30-64-year-old uninsured or Medicaid-insured Ohio breast cancer patients diagnosed 4 years before and 4 years after the state’s 2014 Medicaid expansion (study group); the control group was the privately insured. Time-to-surgery (TTS) was defined as days from diagnosis to surgery. Demographic and treatment variables before and after expansion were examined in multivariate analysis. RESULTS: There was a 10.4% point increase in breast conservation therapy (BCT) in the study group (pre-ACA 26.3%, post-ACA 36.7%; p < 0.01) compared with a 5.8% point increase in the control group (pre-ACA 36.0%, post-ACA 41.8%; p < 0.01). Disparities in reconstruction narrowed between the study (pre-ACA 21.4%, post-ACA 34.5%; p < 0.01) and the control (37.0% pre-ACA, 44.1% post-ACA group p < 0.01) groups. There was no statistically significant change in mean TTS in the study group (pre-ACA 42.1 days, post-ACA 43.1 days p = 0.18) but there was an increase in TTS in the control group (pre-ACA 35.0 days, post ACA 37.0 days; p < 0.01). CONCLUSIONS: Medicaid expansion appears to have narrowed disparities in the utilization of BCT and reconstruction in low-income women. However, there was no improvement in surgical delay.