The Spanish keeper flew to Munich for the op last Thursday.
A statement on the club site read:
"Liverpool today confirmed that Pepe Reina has undergone successful surgery on a double hernia.
"The decision was taken for the Reds keeper to undergo a non-emergency operation in Munich at the end of the season.
"The Spanish international will now begin a rehabilitation programme and is expected to return with the rest of the squad for pre-season training next month."