The truth has been hidden by governments for more than 60 years, the Moon walker says. And he claims he is lifting the lid on a conspiracy to keep aliens a secret.
Dr Mitchell, who was on Apollo 14 in 1971, has told how he was aware of many UFO visits to Earth during his career with Nasa but each one was covered up. The 77-year-old claims the space agency made contact with aliens, describing the beings as "little people who look strange to us".
He said supposedly real-life ETs were similar to the traditional image of a small frame, large eyes and head.
He claimed our technology is "not nearly as sophisticated" as theirs and warned "we would be been gone by now" had the aliens been hostile.
During a radio interview he said: "I happen to have been privileged enough to be in on the fact that we've been visited on this planet and the UFO phenomena is real.
"It's been well covered up by all our governments for the last 60 years or so, but slowly it's leaked out and some of us have been privileged to have been briefed on some of it. I've been in military and intelligence circles, who know that beneath the surface of what has been public knowledge, yes - we have been visited. Reading the papers recently, it's been happening quite a bit."