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BACKGROUND Right hemicolectomy is recommended for appendiceal adenocarcinoma but may not be needed for early-stage disease. OBJECTIVE This study aimed to determine whether appendectomy offers adequate oncologic outcomes for T1 appendiceal adenocarcinoma from a national cohort of patients. DESIGN Patients with T1 appendiceal adenocarcinoma (mucinous and non-mucinous histology) treated with either a right hemicolectomy or appendectomy between 2004-2016 were retrieved. Multivariate Cox-regression analysis was used to identify predictors of overall survival. SETTING National cancer database. PATIENTS A total 320 patients (median age 62yrs, 47% females) were identified: 69 (22%) underwent an appendectomy and 251 (78%) underwent a right hemicolectomy. MAIN OUTCOME MEASURE Overall survival. RESULTS Non-mucinous adenocarcinoma was identified in 194 (61%) while 126 (39%) had mucinous adenocarcinoma. Out of the overall cohort, 43% had well differentiated histology, 39% had moderately differentiated disease and 4% had poorly differentiated tumors. The rate of lymph node metastasis was lower in well differentiated tumors (3%) compared to moderately (10%) or poorly differentiated tumors (25%). On univariate survival analysis, right hemicolectomy was associated with improved 1-,3- and 5-year overall survival in patients with moderately/poorly differentiated disease (P<0.001) but not for well differentiated disease (p=1.000). After adjustment, right hemicolectomy was associated with overall survival improvement for moderately/poorly differentiated T1 adenocarcinoma (HR=0.26, 95% CI: 0.08-0.82, p=0.02) but not for well differentiated disease. LIMITATIONS This study was limited by its retrospective nature. CONCLUSION The current analysis from the national cancer database demonstrates that appendectomy is associated with equivalent survival to right hemicolectomy for well differentiated T1 adenocarcinoma, while for moderately and poorly differentiated disease, right hemicolectomy is oncologically superior to appendectomy. See Video Abstract at http://links.lww.com/DCR/B689.