Background: Conversion surgery in patients with locally advanced esophageal cancer that is not resectable at first time and has responded to prior therapy remains unclear. Recently, the usefulness of RAMIE for locally advanced esophageal cancer has begun to be discussed. In this study, we first analyzed the short- and long-term results of RAMIE, then examined the results of conversion RAMIE in T3br/T4b patients, and compared them with those of conversion using conventional MIE. Methods: Short-term and long-term postoperative outcomes were analyzed in 203 cases of robot-assisted esophageal cancer resection between 2020/1 and 2023/08. In addition, 33 patients with T3br/T4b who were initially diagnosed with cT3br/T4b and who underwent RAMIE after prior treatment were selected and compared to 48 cT3br/T4b cases with conventional MIE performed at the same time. Results: The mean age of RAMIE patients was 66.2 years, male to female ratio 170:33, preoperative treatment including NAC 150:53, and Clinical Stage I:II:III:IV 41:27:97:38. Surgical outcomes included thoracic surgery time of 200.3 min and total blood loss of 154.4 ml. Perioperative outcomes were Clavien-Dindo Grade 1 or higher: suture failure 4.4%, pneumonia 13.3%, and recurrent nerve palsy 16.7%. Long-term prognostic analysis (MST: 483.6days) showed 3yOS:97.6/94.1/80.3/70.9% and 3yDFS:96.2/87.2/66.2/52.4% in cStage I/II/III/IV. Especially in cStage II/III patients, 3yOS: 81.5%, 3yDFS: 71.4%. Long-term outcomes were not significantly different from those of conventional thoracoscopic procedures performed at the same time. Perioperative outcomes in cT3br/cT4b patients at initial presentation were pneumonia: 18.1%, recurrent nerve palsy rate: 12.1% (excluding complicated resection cases), and these 3yOS:66.2% and 3yDFS:48.7%. The 3yOS:52.7% and 3yDFS:40.3% of cT3br/T4b cases in the usual MIE showed a favorable trend in RAMIE (p=002). Of the 38 patients with recurrence after RAMIE surgery, 19 were local/regional and 19 were distant. Of these, 5/6/5/3 were brain/lung/liver/LN+others as the first site of distant metastasis. Conclusions: The short- and long-term results of RAMIE in our department, including T3br/T4, were described, and the short-term and long-term results of RAMIE were considered acceptable. In terms of recurrence, local/regional disease control was considered to be relatively good.