Background: Women with node-positive endometrial cancer have higher rates of disease recurrence and decreased survival compared to those with early stage disease. Adjuvant treatment is considered a mainstay of treatment, yet no standard treatment approach exists. Using a large national cancer database, we aimed to investigate outcomes for women with node-positive endometrial cancer treated with chemotherapy (CT) alone, radiotherapy (RT) alone, or chemoradiotherapy (CRT), compared to patients that received no adjuvant treatment. Methods: The National Cancer Database was queried to identify women with surgically staged IIIC1 or IIIC2 node-positive endometrial cancer diagnosed between 2003 and 2011. Chi-square tests and multivariable logistic regression were performed to analyze factors associated with treatment type. Survival analysis was performed using log-rank test, Cox proportional hazards regression, and Kaplan-Meier estimates. Results: A total of 7,653 patients were identified, among whom 1,502 (19.6%) received no adjuvant treatment, 1,350 (17.6%) received RT, 1,939 (25.3%) received CT, and 2,862 (37.4%) received CRT. Patients were more likely to receive CRT if they were younger, had fewer comorbidities, lived closer to the hospital, had fewer number of positive nodes, had smaller tumor size, and if a single agent chemotherapy regimen was used. Use of CRT was associated with improved survival compared to no adjuvant treatment (HR 2.08, 95% CI 1.73-2.50, p < 0.001), RT only (HR 1.28, 95% CI 1.09-1.51, p = 0.003), and CT only (HR 1.34, 95% CI 1.15-1.56, p < 0.001). Receipt of any treatment was superior to no treatment. Conclusions: In women with node-positive endometrial cancer, modern multimodality CRT appears to confer an additional survival advantage beyond that achieved with CT or RT alone in this large cohort. Our findings suggest that CRT should be the preferred adjuvant treatment strategy in women with node-positive endometrial cancer who are expected to tolerate the toxicities of the combined approach.