As pilot of the lunar module during the Apollo 15 mission in 1971, he drove the first lunar roving vehicle, spending 18 hours on the Moon, travelling over 25 km. He and David Scott collected 77 kg of Moon soil and rocks.

Irwin was a test pilot for the US Air Force before being chosen as an astronaut in 1966. He retired from NASA in 1972. After his retirement, he founded the High Flight Foundation, a Christian organization, and served as its president and chair until his death.