Purpose To evaluate whether inclusion of incidental radiation dose to the cardiac atria and ventricles improves the prediction of grade ≥3 radiation pneumonitis (RP) in advanced-stage non-small cell lung cancer (AS-NSCLC) patients treated with intensity modulated radiation therapy (IMRT) or volumetric modulated arc therapy (VMAT). Methods and Materials Using a bootstrap modeling approach, clinical parameters and dose–volume histogram (DVH) parameters of lungs and heart (assessing atria and ventricles separately and combined) were evaluated for RP prediction in 188 AS-NSCLC patients. Results After a median follow-up of 18.4 months, 26 patients (13.8%) developed RP. Only the median mean lung dose (MLD) differed between groups (15.3 Gy vs 13.7 Gy for the RP and non-RP group, respectively; P=.004). The MLD showed the highest Spearman correlation coefficient (Rs) for RP (Rs = 0.21; P<.01). Most Rs of the lung DVH parameters exceeded those of the heart DVH parameters. After predictive modeling using a bootstrap procedure, the MLD was always included in the predictive model for grade ≥3 RP, whereas the heart DVH parameters were seldom included in the model. Conclusion Incidental dose to the cardiac atria and ventricles did not improve RP risk prediction in our cohort of 188 AS-NSCLC patients treated with IMRT or VMAT.