We describe a 24-year-old construction worker who was unaware that he had been shot by a pneumatic nail gun in the chest during work. After returning home, he felt some palpitations and mild shortness of breath, and in the mirror discovered a non-bleeding pinpoint skin wound in his upper chest. He admitted himself to the emergency department of a local hospital and, after a detailed history and a chest X-ray had been taken, he was surprisingly diagnosed with a penetrating nail injury to the heart and was referred to our center. Transthoracic echocardiography and chest computed tomography were done, and the patient was transported to the operating room. After the nail had been removed and the mitral valve repaired, the patient was discharged on the fifth postoperative day without any complications.