A 39-year-old male who was admitted to emergency department due to cutting and penetrating stab wounds had a 2.5 cm stab wound at the intersection of the left midclavicular line and sixth intercostal space. There was no significant finding on posteroanterior chest X-ray. Thoracic computed tomography which was performed to eliminate thoracic or mediastinal injuries revealed pleural effusion reaching 1 cm in thickness in the pericardial space and a retrosternal hematoma. The patient underwent median sternotomy urgently. After hematoma was removed in the pericardial space, a 1.5 cm laceration along the anterior surface of the left ventricle was seen. Bleeding was managed with finger inserted into the left ventricle. The injury site was repaired primarily with pledgeted 3/0 polypropylene and 2/0 polyethylene polyester sutures. The patient recovered without any complication. Thoracic computed tomography is an important diagnostic tool for cutting and penetrating stab wounds towards the heart.