The actor, who quit the long-running BBC1 science-fiction show last year, joins a cast that also includes Game Of Thrones star Emilia Clarke.
Paramount Pictures said he will play "a new character with a strong connection to John Connor" - the character played by Jason Clarke - in the film which is called Terminator: Genesis.
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Schwarzenegger played the robot assassin of the title role in the original 1984 film which was directed by James Cameron and led to a flurry of follow-ups that cashed in on its cult status.
Millions of viewers tuned in to Doctor Who on Christmas Day to watch Smith hand over the controls of the Tardis to the latest incarnation of the timelord in Peter Capaldi.
The seasonal special, entitled The Time Of The Doctor, brought together threads from across Smith's four-year stint and saw many of his old allies and former foes come together one last time.
The actor said at the time it was the right moment to leave the role, but revealed his mother begged him to carry on in the show.
He said: "It feels very emotional to be doing my final episode. My mother is mortified, honestly, she was at the front of campaigning for me to stay.
"And she wasn't happy when I said I was going to leave. But when you gotta go, you gotta go."