BACKGROUND AND AIMS: Limited data exist regarding the long-term outcomes of endoscopic therapy (ET) with or without chemoradiation therapy (CRT) for T1b esophageal adenocarcinoma (EAC). Our aim was to identify the risk factors for lymph node metastasis (LNM) in T1b EAC and assess how the chosen treatment modality affects overall survival (OS) and cancer-specific survival (CSS). METHODS: We analyzed patients with histologically confirmed T1b EAC diagnosed between 2004 and 2018 using the Surveillance, Epidemiology, and End Results database. Focusing on T1bN0M0 staging, the patients were divided into 2 groups (ET [n = 174] and surgery [n = 769]), and OS and CSS rates were calculated. RESULTS: Of 1418 patients with T1b EAC, 228 cases (16.1%) exhibited LNM at diagnosis. Notable risk factors for LNM included poorly differentiated tumor and lesion size ≥20 mm. For T1bN0M0 cases, ET was commonly performed from 2009 to 2018 (odds ratio [OR], 4.3), especially for patients aged ≥65 years (OR, 3.1) with tumor size <20 mm (OR, 2.3). During the median 50 months of follow-up, age ≥65 years (hazard ratio [HR], 1.9), ET (HR, 1.5), and CRT (HR, 1.4) were associated with poorer OS. Factors linked to decreased CSS were age ≥65 years (subhazard ratio [SHR], 1.6), poorly differentiated tumors (SHR, 1.5), and CRT (SHR, 1.5). CONCLUSIONS: In T1b EAC, tumor size ≥20 mm and poor differentiation are notable risk factors for LNM. ET exhibited comparable CSS outcomes to surgery for carefully selected T1bN0M0 lesions. CRT did not provide additional survival benefit for these lesions; however, large-scale studies are required to validate this finding.