The association between Medicaid expansion and postoperative mortality after surgery for gynecologic cancer is unknown. Our objective was to compare 30- and 90-day postoperative mortality after gynecologic cancer surgery before and after 2014 in states that did and did not expand Medicaid. We searched the National Cancer Database for women aged 40-64yearsold between 2010 and 2016 who underwent surgery for a primary gynecologic malignancy. We used pre/post and quasi-experimental difference-in-difference (DID) multivariable logistic regressions to evaluate mortality pre-2014 (2010-2013) and post-2014 (2014-2016) for states that did and did not expand Medicaid in January 2014. We completed univariable logistic regressions for covariates of interest. Among 169,731 women, 30-day postoperative mortality in expansion states after 2014 significantly decreased for endometrialcancer (odds ratio [OR] 0.42, 95% confidence interval [CI] 0.26-0.67) and ovarian cancer (OR 0.67, 95% CI 0.46-0.99) and increased for cervical cancer (OR 3.82, 95% CI 1.12-13.01). Compared with non-expansion states, expansion states had improved 30-day postoperative mortality for endometrial cancerafter 2014 (DID OR 0.54, 95% CI 0.31-0.96). Univariable analysis demonstrated improved 30-day postoperative mortality for Black women with endometrial cancer in expansion states (DID OR 0.22, 95% CI 0.05-0.95). There was improved 90-day postoperative mortality for endometrial cancer in expansion states (OR 0.66, 95% CI 0.50-0.85), and improved 90-day postoperative mortality for Midwestern women with ovarian cancer in expansion states on univariable analysis (DID OR 0.48, 95% CI 0.26-0.91). State Medicaid legislation was associated with improved postoperative survival in women with endometrial cancer and subgroups of women with endometrial and ovarian cancer.