Background: Implementation of the Affordable Care Act (ACA) has resulted in improvements in cancer outcomes but the extent to which these apply to specific racial and ethnic populations is unknown. We examined changes in health insurance distributions pre- and post-ACA and assessed cancer-specific mortality rates by race and ethnicity. Methods: The population included 167,181 newly diagnosed breast (n = 117,738), colorectal (n = 38,334), and cervix cancer (n = 11,109) patients younger than 65 years and 141,026 patients 65 years or older in the California Cancer Registry. Hazard rate ratios (HRRs) and 95% confidence intervals (CIs) were calculated using multivariable Cox regression to estimate associations with risk of 5-year cancer-specific death for each cancer site pre- (2007-2010) and post-ACA (2014-2017), and by race and ethnicity (American Indian/Alaska Natives, AIAN; Asian Americans; Hispanics; Native Hawaiian/Pacific Islanders, NHPI; non-Hispanic Blacks, NHB; and non-Hispanic whites, NHW). Difference-in-difference analysis was conducted to compare changes over time between younger (< 65 years) and older (65 years and older) patients. Results: Cancer-specific mortality for patients age < 65 was significantly lower post- vs. pre-ACA for colorectal cancer among Hispanic (HRR = 0.83; 95% CI: 0.74-0.93), NHB (HRR = 0.69; 95% CI: 0.58-0.81), and NHW (HRR = 0.90 95% CI: 0.84-0.97) but not Asian American (HRR = 0.95; 95% CI: 0.82-1.10) patients. The HRR for younger NHB colorectal cancer patients was significantly lower than that for patients 65 years of and older (HRR = 1.09; 95% CI, 0.95-1.25, p-interaction < 0.0001). A significantly lower risk of dying from cervix cancer was observed in the post- vs. pre-ACA period among younger NHB women (HRR = 0.68; 95% CI: 0.47-0.99), but this was not significantly different than that for older women (HRR = 0.41; 95% CI, 0.16-1.01, p-interaction = 0.30). No significant differences in breast cancer-specific mortality were observed for any racial or ethnic group. Conclusions: Findings show decreases in cancer-specific mortality for colorectal and cervix cancers for some racial and ethnic groups following ACA implementation in California. These results shed light on ongoing discussions as additional states consider Medicaid expansion. Future studies should assess shifts between health insurance plans resulting from the economic impact of the 2019 novel coronavirus (COVID-19) pandemic.