The aim of this study was to quantify the radiation dose to the corresponding lymph drainage area in esophageal cancer using three-dimensional conformal radiation therapy (3D-CRT) with involved-field irradiation (IFI) and to analyze associated factors. A retrospective analysis of 81 patients with esophageal cancer was conducted. According to the location of the lesions, the lymph drainage area was delineated and the dosimetric parameters were calculated. The 1-, 3-, 5- and 8-year survival rates of the patients were 67.90, 33.33, 20.99 and 11.11%, respectively. Based on the dose-volume histogram in the treatment plan, we calculated the volume percentage of the planning target volume including clinically positive lymph nodes (PTV-N) receiving radiation doses of 30, 35, 40, 45 and 50 Gy (VPTV-N30-50). The median values of VPTV-N30-50 were 73,70, 67, 64 and 58%, respectively. The prescribed dose size exhibited no correlation with VPTV-N30-35, but did exhibit a significant correlation with VPTV-N40-50; the radiation field was not correlated with VPTV-N30-45, but exhibited a significant correlation with VPTV-N50; the length of the lesion on esophageal barium meal X-ray and the PTV were significantly correlated with VPTV-N30-50. The analysis of variance revealed that the VPTV-NX value in the upper thoracic segment was higher compared with that in the middle and lower thoracic segments; VPTV-N30-35 values differed significantly according to the different locations of the lesions, whereas VPTV-N40-50 values exhibited no significant differences. The value of VPTV-NX exerted no significant effect on long-term patient survival. Therefore, the corresponding lymph drainage area of esophageal cancer is subjected to a certain radiation dose when patients undergo 3D-CRT with IFI, which may play a role in the prevention of regional nodal metastasis. However, this hypothesis requires confirmation by further clinical studies.