Seattle announced the deal Thursday. To make room on the 40-man roster, Seattle designated for assignment reliever Shawn Kelley, who just last week agreed to a 1-year, $935,000 deal with the team to avoid arbitration. Seattle has 10 days to trade or release Kelley, or to send him outright to the minors if he clear waivers.
Shoppach played for Boston and the New York Mets last season, appearing in 76 games. The 32-year-old also has a relationship with Seattle manager Eric Wedge, having played for him in Cleveland for parts of four seasons from 2006-09. Montero and Shoppach are the only two catchers on Seattle's 40-man roster.
Shoppach can earn an additional $500,000 in performance bonuses.
Kelley went 2-4 with a 3.25 ERA in 47 appearances last season for Seattle.