AbstractBackgroundCardiac rupture is rare but has a high mortality rate. Cardiac rupture due to blunt trauma is generally caused by the heart being pinched into the bony thorax.Case PresentationA 90‐year‐old man in shock was transported to the hospital after his precordium was stepped on by a cow. He developed right atrial rupture from penetration of the heart by fractured and calcified costal cartilage, with massive hemothorax, hemorrhagic shock, and respiratory failure. We immediately performed cardiac injury repair. The patient was discharged without sequelae.ConclusionEmergency physicians should be aware that secondary cardiac rupture can show a penetrating injury‐like presentation due to calcified costal cartilage caused by blunt chest trauma.