Endoscopic submucosal dissection (ESD) has been widely accepted for treating superficial esophageal squamous cell carcinoma (SESCC). The aim of this study was to evaluate the efficacy and safety of ESD for SESCC and the effect of different sedation methods on their clinical outcomes. We retrospectively analyzed a total of 169 patients (175 lesions) who underwent ESD for SESCC at Samsung Medical Center, Seoul, South Korea. Short-term and long-term clinical outcomes were evaluated and compared according to the sedation method (conscious sedation [CS] vs general anesthesia [GA]). En bloc resection, complete resection, and curative resection (CuR) were achieved in 93.7, 74.9, and 58.9% of cancers, respectively. Perforation and stricture occurred in 8.0 and 12.0% of lesions, respectively. During a mean follow-up period of 33.7 months for survival, 3 (3.0%) patients died without evidence of recurrence after achieving CuR. During a mean follow-up period of 32.5 months for recurrence, 1 (1.0%) patient experienced lymph node metastasis. Synchronous and metachronous cancer were found in 1.0% and in 3.0% of patients, respectively. Multivariate analysis revealed that GA was associated with a higher complete resection rate and a lower perforation rate as compared to CS (odds ratio 3.401, 95% confidence interval 1.317–8.785, P = 0.011 and odds ratio 0.067, 95% confidence interval 0.006–0.775, P = 0.030, respectively). ESD is an oncologically effective treatment modality for SESCC, particularly when CuR is achieved. Applying GA for esophageal ESD could improve the clinical outcomes of ESD in patients with SESCC.