Beyond his achievements as an astronaut with NASA, Irwin is perhaps most notable for his attempts to use his experiences on the Moon to spread his belief in Christianity. He publicly commented many times about how his experiences in space had made the presence of God even more real to him than before.

In 1982, Irwin led an expedition to Mount Ararat, Turkey in search of the remains of Noah's Ark. The expedition failed to find any sign of the Ark. He was he was injured during the decent and had to be carried for part of the way.