Screenings are an important public health intervention to prevent breast and cervical cancer. Previous studies have indicated a relationship between Medicaid expansion under the Affordable Care Act (ACA) and breast and cervical cancer screenings, but the results have been mixed and inconclusive. We examined the relationship between Medicaid expansion and breast and cervical cancer screenings among low-income women. In our secondary analyses, we assessed if this association was modified by race/ethnicity or rural residence status. We used data from the Behavioral Risk Factor Surveillance System from 2012-2019, excluding 2017. States that expanded Medicaid before the ACA were excluded. A total of 27 states were considered Medicaid expansion states and 17 were considered non-expansion states. Participants included women with incomes up to 138% of the Federal Poverty Level (FPL) without a previous cancer diagnosis, excluding Medicare-eligible ages. Using a difference-in-difference time series event design, this study compared the odds ratio of breast and cervical cancer screenings for a total of 8 years pre- and post-Medicaid expansion controlling for age, race/ethnicity, education, income, employment, having a regular healthcare provider, rurality, and year and state fixed effects. Dummy variables on years from expansion were created from 7 years before expansion up to 5 years after expansion, including a dummy variable indicating the expansion year. The expansion year dummy variable was coded as 1 if the year of observation was equivalent to the year when the state expanded Medicaid and 0 otherwise. Stratified analyses were used to test if there was an interaction at the multiplicative level by race/ethnicity or rurality. Among 27,290 women aged 40-64, 76.4% of the women residing in expansion states reported having an up-to-date breast cancer screening compared to 70.8% of women residing in non-expansion states. Among 30,808 women aged 18-64, 82.3% of the women residing in expansion states reported having an up-to-date cervical cancer screening compared to 79.9% of women residing in non-expansion states. Medicaid expansion was associated with 2.89-fold higher rate of up-to-date breast cancer screenings 1 year post-expansion (aOR 2.89; 95% CI: 1.34, 6.23). The odds ratios relating Medicaid expansion and up-to-date cervical cancer screenings during the expansion year and 4 years post-expansion were 1.35 (95% CI: 1.14, 1.61) and 1.37 (95% CI: 1.01, 1.85), respectively. The associations were stronger among White non-Hispanic, Black non-Hispanic women, and urban women for both breast and cervical cancer screenings. Medicaid expansion led to higher rates of up-to-date breast and cervical cancer screenings during some years pre- and post-expansion. These associations were modified by race/ethnicity and rurality. Future research should control for baseline rates of up-to-date breast and cervical cancer screening rates. A longitudinal study should be conducted to further control for time-varying confounders. Findings support adoption of Medicaid expansion should be adopted by all states to improve breast and cervical cancer screening rates for low-income women.