The Boeing AH-64 combat helicopter crashed into a residential neighbourhood of Kanzaki in Saga, Japan.
The house was engulfed in flames and emergency services rushed to the scene.
Officials said the four occupants of the house were not home when the chopper crashed into the building, destroying the roof.
The helicopter was involved with the nearby Ground Self-Defence Force’s Metabaru training camp.
The pilot and crew member have both been injured and suffered heart and lung failure, a spokesman for the local government said.
Defence Minister Itsunori Onodera said the helicopter lost contact with air traffic control before crashing int the house.
Prime Minister Shinzo Abe has instructed all similar helicopter to be grounded until after an investigation.