Rauch can earn an additional $750,000 based on how many days he is on Miami's active roster. He can earn an additional $250,000 each for 90, 120 and 150 days.
The 6-foot-11 Rauch had a 3.59 ERA in 73 games with the Mets last season. He was 3-7 with four saves in eight opportunities.
The 34-year-old Rauch is 42-38 with 62 saves and a 3.80 ERA in 10 seasons. He began his career with the White Sox in 2002, and he set a career high with 21 saves for Minnesota in 2010.
The Marlins designated outfield Bryan Petersen for assignment on Tuesday to clear room for Rauch on the 40-man roster.