Salas, 31, also can earn $350,000 in incentives. The deal is pending until Salas passes a physical.
Salas posted a 2.08 ERA in 17 games with the Mets last season after being acquired from the Los Angeles Angels.
The veteran has a 19-22 record and 3.64 ERA in seven seasons with the St. Louis Cardinals, Angels and Mets. He also provides extra insurance as a possible fill-in closer with Jeurys Familia facing a likely suspension over a domestic violence incident.
New York also signed veteran left-hander Tom Gorzelanny to a minor league contract with an invitation to spring training. Gorzelanny will reportedly make $1 million if he makes the Mets' roster and could earn another $1.8 million in incentives.