The purpose of this study was to evaluate the feasibility of small primary gross tumor volume (GTV)-to-clinical target volume (CTV) margin expansion in neoadjuvant chemoradiation for esophageal squamous cell carcinoma. Medical records of 139 patients with locally advanced esophageal squamous cell carcinoma who underwent neoadjuvant chemoradiation and radical esophagectomy were retrospectively reviewed. Patients treated with longitudinal primary GTV-to-CTV margin expansion of 2 cm and no additional expansion of the CTV through the esophagus were classified into a small margin (SM) group (37 patients). The remaining 102 patients were classified as a large margin (LM) group. Patterns of recurrence including local and out-field regional recurrence rates were compared between the two groups. Clinical outcomes including rates of local control, regional control, failure-free survival, and overall survival were also compared. More patients in the SM group underwent paclitaxel + carboplatin, Mckeown esophagectomy, and intensity-modulated radiation therapy than in the LM group. With a median follow-up of 25.6 months, there was no significant difference in the crude rate of local recurrence (10.8% vs. 6.9%, P=0.694), out-field regional recurrence (27.0% vs. 19.6%, P=0.480), or out-field regional recurrence without in-field recurrence (10.8% vs. 12.7%, P=0.988) between the two groups. There was no significant difference in failure-free survival (5-year, 34.4% vs. 30.6%, P=0.652) or overall survival (44.1% vs. 38.5%, P=1.000), either. Esophageal fistula was not reported in the SM group (0.0% vs. 7.9%, P=0.176). In conclusion, a radiation field with 2 cm of longitudinal primary GTV-to-CTV was feasible in the neoadjuvant setting for esophageal squamous cell carcinoma treatment.