The War of the Worlds star told a German newspaper he did not believe humans were alone in the universe.
When asked by tabloid daily Bild whether that meant he believed in aliens, Cruise said: "Yes, of course."
Cruise is an outspoken follower of Scientology, founded by science fiction writer L Ron Hubbard.
Some critics say the faith is based upon a story about alien visitors to Earth.
Cruise told the German newspaper: "Are you really so arrogant as to believe we are alone in this universe?
"Millions of stars, and we're supposed to be the only living creatures? No. There are many things out there, we just don't know."
War of the Worlds, based on British writer HG Wells' 1898 story of the invasion of Earth by Martians, is due to open in the UK on Friday.
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