The actor and former bodybuilder believes that the ex-Manchester United star is in "great shape", but does not expect Ronaldo to be competing in any bodybuilding contests.
"He has a fantastic physique," Schwarzenegger told COPE. "He has some great abs, he looks spectacular.
"He looks to be in great shape, so it is clear he's a great footballer. I don't think he'd be interested in competing in a Mr Olympia."
The 66-year-old was speaking in Madrid ahead of the opening of his 2013 Arnold Classic bodybuilding competition.