Cardiotoxicity is a known consequence of thoracic irradiation and there are multiple overlapping risk factors for cardiac disease and thoracic malignancies. In this study, we quantified the impact of thoracic (chemo)radiation on cardiac troponin T (TnT), creatine kinase-myocardial band (CK-MB) and aminoterminal pro-brain natriuretic peptide (NT-proBNP). Thirty patients receiving radiation therapy to the thorax with or without concurrent chemotherapy were evaluated. Serum was collected at baseline, 2 weeks into treatment and at the completion of radiation therapy. TnT, CK-MB and NT-proBNP were quantified using commercially available immunoassays. Cardiac dosimetric parameters and clinical risk factors were examined. In 29 of 30 patients, serum TnT remained undetectable (<0.01ng/mL) throughout (chemo)radiation. In the one patient with detectable serum TnT, levels did not change significantly with treatment. Similarly, thoracic (chemo)radiation did not cause statistically significant elevations in serum CK-MB and NT-proBNP. Thus, contemporary thoracic (chemo)radiation does not commonly result in elevations of serum TnT, CK-MB or NT-proBNP. Elevations in these markers during treatment merit further evaluation.