Background EBRT in resected, nonmetastatic anaplastic thyroid cancer (ATC) remains undefined. We evaluated patterns/outcomes with EBRT and chemotherapy in this setting. Methods This retrospective analysis included patients identified from the National Cancer Database with nonmetastatic ATC from 2004 to 2014 who underwent non‐palliative resection. Results Our analysis included 496 patients, including 375 who underwent adjuvant EBRT (among whom 198 received concurrent chemotherapy). The median age was 68 years. On MVA, EBRT was associated with sex (OR 0.5, 95% CI 0.3‐0.8, P = .002) and income (OR 2.2, 95% CI 1.4‐3.3, P < .001). EBRT was associated with longer OS on UVA (12.3 vs 9.1 months, P = .004) and MVA (HR 0.7 CI 0.6‐0.9, P = .004). Concurrent chemoradiation was associated with longer OS on UVA (14.0 vs 9.1 months, P = .003) and MVA (HR 0.6 CI 0.5‐0.8, P < .001). Conclusion Adjuvant EBRT is associated with longer OS in resected, nonmetastatic ATC, with additional improved survival with concurrent chemotherapy.