Rauch, 34, pitched for the Mets last season. He compiled 57.2 innings pitched and an ERA of 3.59 as a set-up man in the Mets' bullpen.
Bryan Petersen was designated for assignment to make room for Rauch.
Rauch should be a middle reliever for the Marlins in 2013, but could get some time in the later innings if injuries set in.
The Marlins continue to make small acquisitions despite their recent fire-sale, which may show that the team is still going to attempt to put a semi-productive team on the diamond come April.
He dealt with various injuries throughout the 2012 season, but pitched through them. He was one of the few consistently effective relievers the Mets had last season.