Aldrin, the second man on the moon, and four others gave accounts of their sightings under strict lab conditions.
He, Al Worden, Edgar Mitchell and Gordon Cooper all took part in the study conducted by the Institute of BioAcoustic Biology in Albany, Ohio.
Aldr in, 88, claimed he was a spaceship on his way to the moon, adding: "There was something out there that was close enough to be observed... sort of L-shaped."
The tests, reportedly more reliable than standard lie detector tests, showed he was telling the truth, the Daily Star reported.
Apollo 15 pilot Worden, 85, and Apollo 14's Mitchel also claimed to have seen UFOs while Cooper says he actually tried to chase a cluster of objects.
Tests analysing their voice patterns suggested they were also telling the truth about their strange encounters.
Aldrin answered questions about his alleged encounter with alien life on a Reddit Q&A with fans last week.
In one post he said: "On Apollo 11 in route to the Moon, I observed a light out the window that appeared to be moving alongside us.
"There were many explanations of what that could be, other than another spacecraft from another country or another world.
"It was either the rocket we had separated from or the four panels that moved away when we extracted the lander from the rocket.
"It was not an alien. Extraordinary observations require extraordinary evidence. That's what Carl Sagan said.
"There may be aliens in our Milky Way galaxy, and there are billions of other galaxies. The probability is almost certain that there is life somewhere in space.
"It was not that remarkable, that special, that unusual, that life here on earth evolved gradually, slowly, to where we are today."
On July 21, 1969, Neil Armstrong made history by becoming the first person to set foot on the earth’s moon.
Upon landing, he is famously quoted as saying: "That's one small step for man, one giant leap for mankind."
Buzz was on the same mission, Apollo 11, as Neil Armstrong and soon followed in his footsteps - making him the second man on the moon.Alien hunters claim they have found a crashed spaceship on remote island
In total, Neil and Buzz were on the lunar surface for only 21 hours, 36 minutes and 21 seconds.
Pete Conrad was a moon walker on the Apollo 12 mission, which launched on November 14, 1969. He was partnered by Alan Bean.
Also on the Apollo 12 mission, was Alan Bean. He and Pete were on the moon for two days - November 19 and 20, 1969.