Patterson, 33, last appeared in the Major Leagues in 2008 with the Padres - he allowed one hit in 3 1/3 innings over three appearances. He has appeared in just four Major League games in his career - all in 2008 with the Padres and Yankees. He pitched to a 1.93 ERA over 4 2/3 innings with both teams that season.
Patterson has been in the Mariners minor league system since 2010. He was 1-3 with a 2.89 ERA in 26 relief appearances for Triple-A Tacoma this season.
Patterson will report to Triple-A Buffalo.