We report a 1-year-old boy with a delayed diagnosis of traumatic ventricular septal defect (VSD) related to chest compression. His cardiac function was stable after adequate medical treatment. Spontaneous closure of traumatic VSD occurred to this patient at the age of 4 years. This is a rare case of traumatic VSD associated with accidental chest compression, which is similar to rupture of the ventricular septum after blunt chest trauma. It should be kept in mind that traumatic VSD and concomitant thoracic injuries can develop during chest compression. The clinician should pay attention to the potential risk of traumatic VSD in patients experiencing chest compression. Echocardiography is a convenient and effective tool for serial follow-up examination and avoiding the delayed diagnosis. Troponin I level can be a useful screening test. Conservative management of traumatic VSD with hemodynamic stability is recommended because of possible spontaneous closure.