Arrieta, 29, overtook early favorite Zack Greinke, winning his final 13 starts. His only post-All-Star break defeat came when the Cubs were no-hit by the Philadelphia Phillies in late July. Arrieta went 14-1 with a 0.75 ERA over the final three months, the lowest second-half ERA in history for a starting pitcher (minimum 12 starts).
His second half included a no-hitter in August against the Los Angeles Dodgers with the other two finalists for the NL Cy Young, Greinke and Clayton Kershaw, watching from the other dugout. Overall, Arrieta struck out 236 in a career-high 229 innings while leading the league in wins, complete games (four) and shutouts (three). He also gave up the fewest hits (5.9) and home runs (0.4) per nine innings pitched.
Arrieta got 17 first-place votes for 169 points from the Baseball Writers’ Association of America. Greinke drew 10 first-place votes and had 147 points. Kershaw had the other three firsts and 101 points.
Greinke posted a 1.66 ERA that was the lowest in the majors since 1995. He went 19-3, fanned 200 and had a scoreless streak of 45 2/3 innings.
Kershaw had won three of the previous four NL Cy Youngs. He struck out 301, the most in the majors since 2002, and went 16-7 with a 2.13 ERA for the NL West champions.
The Cubs acquired Arrieta in July 2013 in a multiplayer deal that is perceived as one of the best in recent baseball history. The Cubs sent pitcher Scott Feldman and catcher Steve Clevenger to the Baltimore Orioles for Arrieta and reliever Pedro Strop, both of whom helped the Cubs to the playoffs this season for the first time since 2008.
Arrieta is the first Cubs pitcher to win the Cy Young since Greg Maddux in 1992 and the fifth Cubs winner overall, also joining Fergie Jenkins (1971), Bruce Sutter (1979) and Rick Sutcliffe (1984).
Arrieta’s win gives the Cubs three postseason awards in three days, as third baseman Kris Bryant won rookie of the year Monday and skipper Joe Maddon took home manager of the year Tuesday.
The Associated Press contributed to this report.