The 29-year-old finished first in the American League in ERA (1.64), and was second in wins and innings pitched (44). He struck out twice as many, 26, as he walked.
No Mariners' pitcher had gone 5-0 in a month since Felix Hernandez in 2009. Last month, Hernandez went 3-0 with a 2.03 ERA and also received votes for the award.
Vargas' first start of the month came on the first day of the month, and he gave up one run to the Red Sox in eight innings at Safeco Field. That was a no-decision. His next three starts came on the road, and he allowed a combined four runs in 21 innings against the A's, Royals and Rays. He finished up the month at home with a combined three runs allowed in 15 innings against the Royals and Blue Jays.
Vargas is 12-7 with a 3.71 ERA and 100 strikeouts in 153 innings and 23 starts in 2012. This is his fourth year with the Mariners, and the one-time second round pick in the Draft (2004, Marlins) is establishing himself as one of the league's top pitchers without high strikeout numbers.