Objectives. Sessile nonampullary duodenal tumors (SNADTs) are relatively rare and endoscopic resection of these lesions is considered more challenging than in other parts of the gastrointestinal tract. The aim of this study was to evaluate the feasibility of endoscopic resection for SNADT. Methods. Medical records including endoscopic resection for SNADT from July 2002 to July 2013 from 5 centers affiliated to The Catholic University of Korea were reviewed retrospectively. Demographic features and clinical outcomes such as complete resection and complications were analyzed. Results. A total of 56 lesions from 54 patients were enrolled in this study. Forty-five lesions were resected by endoscopic mucosal resection (EMR), 6 lesions by endoscopic submucosal dissection (ESD), and 5 lesions by simple polypectomy. Histologic examination after endoscopic resection revealed adenocarcinoma in 2, low grade adenoma in 25, high grade adenoma in 11, and carcinoid tumor in 18 lesions. En bloc resection rates and histological complete resection rates were 78.6% (44/56) and 80.0% (28/35), respectively. Bleeding which required additional endoscopic intervention occurred in 1.8% (1/56) and perforation in 7.1% (4/56). There was no procedure-related mortality. Conclusions. Endoscopic resection techniques including ESD might be safe and effective modalities for the management of SNADT.