Montero and Kendall Graveman were traded from the Mariners to the Astros on Tuesday in exchange for Abraham Toro and Joe Smith, Brian McTaggart of MLB.com reports.
Montero was designated for assignment by the Mariners on Friday, and he'll join the Astros instead of going through the waiver wire. The 30-year-old converted seven of 13 save chances this season and has struggled with a 7.27 ERA, 1.64 WHIP and 37:15 K:BB across 43.1 innings.