OBJECTIVE There are limited data regarding clinical and treatment factors associated with radiation pneumonitis (RP) in patients receiving taxane-based trimodality therapy for esophageal cancer. The purpose of this study was to identify predictors of RP in patients undergoing trimodality therapy. METHODS We retrospectively reviewed patients undergoing chemoradiation followed by esophagectomy between 2006 and 2011. The association between clinical and dosimetric factors with RP was assessed using χ2 test and Mann-Whitney U test. Multivariable regression was used to assess the relationship between grade 2+ RP and clinical/dosimetric factors. Receiver operator curves were generated to identify threshold doses for RP. RESULTS A total of 139 patients were included; 19 (13.7%) patients experienced grade 2+ RP. Patients with upper/middle thoracic tumors (P = .038) and receiving higher radiation doses (P = .038) were more likely to develop grade 2+ RP. There was no association between taxane-based therapy and grade 2+ RP (P = .728). The percent volume of lung receiving 5 Gy (V5; P < .001), 10 Gy (P < .001), 20 Gy (V20; P < .001), and 30 Gy (P < .001) was associated with an increased risk of grade 2+ RP. On multivariable regression, the lung V5 (odds ratio, 1.101; 95% confidence interval, 1.1014-1.195) and V20 (odds ratio, 1.149; 95% confidence interval, 1.1015-1.301) remained associated with grade 2+ RP. A V5 ≤65% and V20 ≤25% were identified as optimal thresholds for increased grade 2+ RP. CONCLUSIONS Dosimetric parameters are strong predictors of symptomatic RP in patients undergoing trimodality therapy for esophageal cancer. Mitigating the risk of RP in these patients should be an important consideration during treatment planning.