To assess risk factors and the extent of pulmonary hemorrhage complicating radiofrequency ablation (RFA) of pulmonary neoplasms. This retrospective study involved 248 ablation sessions for lung tumors (20 primary lesions and 228 metastatic lesions) in 164 patients (mean age 59.7 years, SD: 10.2). Both unipolar and bipolar radiofrequency systems were used under CT fluoroscopic guidance. Extent and underlying factors associated with development of pulmonary hemorrhage were analyzed. Incidence of intra-parenchymal pulmonary hemorrhage, pleural effusion, and hemoptysis were 17.7% (44/248 sessions), 4% (8/248 sessions), and 16.1% (40/248 sessions), respectively. Death because of massive bleeding occurred in one session (0.4%). Significant risk factors associated with intra-parenchymal hemorrhage included: lesions of < 1.5 cm diameter (P = 0.007); basal and middle lung zone lesions (P = 0.026); increased needle track distance traversing the lung parenchyma > 2.5 cm (P = 0.0017); traversing pulmonary vessels in the track of ablation (P < 0.001); and the use of multi-tined electrodes (P = 0.004). Concomitant incidence of pulmonary hemorrhage and pneumothorax was 29.2% (14/48 sessions). While typically safe, RFA of pulmonary neoplasms can result in pulmonary hemorrhage ranging from mild to life-threatening. Management of this complication is mainly preventive through adequate patient selection for ablation therapy and exclusion of technically avoidable risk factors.