The 31-year-old right-hander led the American League in wins (18) and ERA (2.25). Additionally, Kluber's 8.0 WAR was tops among pitchers in both major leagues.
Despite spending a month on the disabled list, Kluber threw more than 203 innings, as he went at least six full innings in 25 of his 29 starts this season. He also tied for the major league lead with five complete games this season.
Kluber, who won the 2014 AL Cy Young, turned around his 2017 performance in order to collect his second award.
After a May 2 outing in which he lasted just three innings, Kluber's ERA stood at 5.06. That start was followed by a DL stint; when Kluber came back, he was lights out, going 15-2 from his June 1 return until the end of the regular season. During that stretch, Kluber led the majors in wins (15), ERA (1.62), WHIP (0.76) and walks per nine innings (9.7).
"Winning a second one maybe, for me personally, kind of validates the first one," Kluber said of winning his second Cy Young.
At one point in the season, Sale seemed like a shoo-in to win his first Cy Young Award. However, while Kluber got better as the season wore on, Sale got worse. The Boston ace's ERA in August and September was 4.09, tied for 54th among 97 pitchers with at least 50 innings. After allowing 11 home runs through his first 21 starts, Sale gave up 13 in his last 11 starts.
Kluber's teammate Carlos Carrasco finished fourth in the voting, as the Indians posted the best ERA in the majors at 3.30.
Kluber is one of four Cy Young Award winners in Cleveland's history, but the first to twice earn the honor.
Information from ESPN's Scott Lauber contributed to this report.