The 33-year-old has negotiated the end of his central England contract with the England and Wales Cricket Board and will now spend part of the English summer season turning out for the county he has sporadically represented since 2010.
"Once the IPL (Indian Premier League) and his IPL commitments are over he is available for Surrey," Surrey Director of Cricket Alec Stewart told the county's You Tube channel on Monday.
"That's predominantly a Twenty20 agreement but that is not to say we won't see him in the four-day game or the 50-over game."
Pietersen, cast away by England last week after their 5-0 Ashes whitewash in Australia because of his perceived lack of team spirit, will mainly feature in the T20 Blast that is scheduled on Fridays from May to July.
"I'm absolutely delighted to have agreed terms with Surrey and am thoroughly looking forward to playing my cricket for the club this summer," Pietersen said in a club statement.
"I've had some of my best moments in cricket at the Oval and I'm really excited at the prospect of getting back out there playing in what will hopefully be a brilliant summer for us all at Surrey."
(Writing by Mark Meadows; Editing by Ken Ferris)
