Achalasia is considered to be a high-risk factor for the development of squamous cell carcinoma. Advances in endoscopic imaging facilitate the detection of superficial esophageal squamous cell carcinoma (SESCC). Little is known about the safety, efficacy, and postoperative course of endoscopic resection for SESCC in patients with achalasia. We have performed over 1500 per-oral endoscopic myotomy procedures for esophageal achalasia and its related diseases. We performed endoscopic resection for 14 patients with 25 SESCCs and conducted follow-up endoscopy after the treatment. The aim of this study was to evaluate the clinical outcomes of endoscopic resection for achalasia-associated SESCC. We conducted a retrospective cohort study of patients with achalasia-associated SESCC who underwent endoscopic resection at our university hospital from August 2010 to November 2017. SESCC was defined as high-grade intraepithelial neoplasia (HGIN) and squamous cell carcinoma in which invasion was confined to the submucosal layer. The patients were followed up with endoscopy at least once a year after endoscopic resection. The therapeutic outcome of endoscopic resection was determined by the last follow-up endoscopy and a telephone survey. Fourteen patients with achalasia underwent endoscopic resection for 25 SESCC lesions. There were 8 men and 6 women, and their median age was 62 years old (range, 43-83). The median disease duration was 20 years (range, 5-50). Sigmoid-type achalasia was seen in 9 cases (64%). Five patients (36%) had no prior history of smoking or drinking. We performed endoscopic resection (ESD/EMR, 23/2) in all cases. None of the patients experienced severe adverse events. The median tumor diameter was 26 mm (range, 7-70). The histological tumor depth of T1a-M (incl. HGIN)/T1b-SM was 24/1. Six patients (43%) had multiple neoplastic lesions. The en bloc resection rate was 100% (25/25), and the R0 resection rate was 96% (24/25). The median duration of follow-up surveillance was 19 months (range, 4-93). We found one case of recurrence in a patient who had undergone ESD. In this case, 2 recurrent tumors were mucosal carcinomas (T1a-EP and T1a-LPM) and were identified near the ESD scar 43 months after ESD. We performed successful ESD for the 2 recurrent tumors. No recurrence was found after ESD in any patient. None of the patients died during the study period. Endoscopic resection is suggested a safe and effective treatment for achalasia-associated SESCC with favorable outcomes.