Elisangela Borborema Rosa, 28, underwent emergency surgery to remove the harpoon, in what doctors called a "bizarre event", with the woman avoiding fatal wounds by a centimetre (0.4 inches.)
Officials said the incident happened when her husband was in the living room cleaning his spear gun, which he used for underwater fishing. The weapon fired towards Ms Rosa, who was in the kitchen at the time, piercing her through the jaw and entering her spinal column.
The woman was taken to a local hospital but was immediately transferred to a regional hospital in nearby Araruama, where a she underwent emergency surgery.
Although the woman is expected to make a full recovery, Neurosurgeon Allan da Costa explained how close the bolt was to causing fatal injuries.