Background: The standard of care for stage I (T1/2N0M0) rectal adenocarcinoma is surgery alone. We investigated practice patterns and outcomes associated with administration of radiotherapy (RT) to surgery for stage I rectal adenocarcinoma. Methods: Using National Cancer Database from 2004 to 2014, 12494 patients with clinical stage T1-2N0M0 rectal adenocarcinoma who had definitive surgery were analyzed. 8265 received definitive surgery alone and 4229 received definitive surgery with preoperative or postoperative RT. Between groups, demographic, tumor and treatment characteristics were compared. Multivariate logistics regression was used to examine factors associated with the receipt of RT. Overall survival (OS) were estimated by Kaplan-Meier method; the log-rank test was used to compare survival curves. Cox proportional hazards modeling determined variables associated with death. Results: Of 12494 patients, 34% received RT; among them, 94% received chemotherapy (CT). Patients who received RT tended to be younger, male, diagnosed in early years, covered by Medicaid/Medicare/Not Insured, treated at community cancer program, a lower Charlson/Deyo score, a T2 clinical stage, a poorly differentiated or a larger tumor. Survival analysis revealed no difference in patients with or without RT (Median survival of 142 months vs. 137 months and 5 year OS of 79% vs. 82%, p = 0.50). Multivariate Cox models showed that variables significantly associated with increased hazard of death (p < 0.05) were older age (HR = 1.06), male gender (HR = 1.24) , Charlson/Deyo score 1 (HR = 1.54)/ Charlson/Deyo score 2 (HR = 2.29) (vs. Charlson/Deyo score 0), clinical T2 stage (HR = 1.15), pathological III/IV stage (HR = 4.16), poorly differentiated grade (HR = 1.38), Medicaid (HR = 1.70) /Medicare (HR = 1.24) /Not Insured (HR = 2.28) (vs. private insurance), community cancer program (HR = 1.17) and lower income (HR = 1.25). After adjusting for all above variables, RT or CT was not associated with improved OS. Conclusions: Addition of RT (with or without chemotherapy) to definitive surgery was not associated with survival advantage in stage I rectal adenocarcinoma.