Schwarzenegger, 67, confirmed the news during a chat with TheArnoldFans.Com in Budapest, reported Ace Showbiz.
When asked if he would return to the upcoming movie's follow-up, he answered, "Yes, of course, next year."
'Terminator Genisys' is set for release in the US on July 1 and features appearances from Jason Clarke, Emilia Clarke, Jai Courtney and JK Simmons among others.
Alan Taylor has directed the film.