Cardiopulmonary resuscitation (CPR) is an irreplaceable option in patients with sudden cardiac arrest. However, lifesaving CPR can also put the patients and treating physicians in a predicament with certain rare and life-threatening complications due to chest wall injuries. Hemothorax is one of such complications which must be diagnosed and treated as early as possible, more importantly in patients with acute coronary syndrome (ACS) as a cause of cardiac arrest, wherein antithrombotic drugs are on board. Possible sources of bleeding in hemothorax can be injury to the internal mammary artery (IMA), intercostal arteries, or rarely azygos vein. Careful evaluation for the source of the bleeder is necessary as often bleeders may be missed out in early phase of evaluation due to associated hemodynamic factors such as low mean arterial pressure, raised intrathoracic pressures, and vasospasm. Here, we report a case of ACS with sudden cardiac arrest revived by CPR and primary percutaneous coronary intervention who eventually developed hemodynamically significant hemothorax due to the right IMA injury as detected by catheter-mediated angiography, which was subsequently sealed by vascular microcoils at either ends of the perforated segment.