BACKGROUND Secondary malignant tumor of the heart is one of the most life-threatening complications of lung cancer. Several published case reports have documented non-small cell lung cancer (NSCLC) patients with neoplastic cardiac invasion. However, the number of reported cases of small cell lung cancer (SCLC) with neoplastic cardiac invasion is limited. CASE REPORT We present a rare case of advanced SCLC in a patient with asymptomatic neoplastic cardiac invasion. We also discuss radiation therapy modalities that should be considered in SCLC patients with cardiac invasion. CONCLUSIONS Clinicians should be vigilant about cases of SCLC with asymptomatic intra-cardiac invasion and practice caution when diagnosing, as well as treating with radiation as a monotherapy.