Purpose: To investigate the prognosis of esophageal squamous cell carcinoma with a microscopically incomplete (R1) resection margin following an esophagectomy, as well as the impact of adjuvant treatment on survival. Methods: Data obtained from 124 patients with R1-resected ESCC were reviewed. The impact of clinicopathological factors and adjuvant treatment on the overall survival, locoregional recurrence, and distant recurrence were explored. Results: For a median follow-up time of 16.8 months, the median overall survival of 124 patients was 25.6 months. The 1, 3, and 5-year overall survival rates were 75.6%+/- 4.0%, 35.9%+/- 5.1%, and 23.2%+/- 5.0%, respectively. Adjuvant therapy was administered in 78 patients. In the univariate analyses, patients with a pN0 stage (log rank, p=0.028) and adjuvant chemotherapy (log rank, p=0.032) exhibited more favorable overall survival. In the multivariate analyses, the pN stage (HR=2.192, p=0.004) and adjuvant chemotherapy (HR=0.032, p=0.004) were independent prognostic factors for overall survival. Locoregional recurrence was the main failure pattern after R1 resection. The pN stage (HR=2.567, p=0.009) and adjuvant radiotherapy (HR=0.278, p=0.000) were independent prognostic factors for locoregional recurrence. Conclusion: In R1-resected esophageal squamous cell carcinoma, adjuvant radiotherapy reduced locoregional recurrence; however, it did not improve overall survival. Adjuvant chemotherapy demonstrated benefits for overall survival. The pN stage was an independent prognostic factor for locoregional recurrence and overall survival.