The 2017 season was Vargas's fourth year with the Kansas City Royals, and his first full season since undergoing Tommy John surgery. Vargas started strong, going 12–3 in the first half, and was named to the American League All Star team for the 2017 Major League Baseball All-Star Game. It was the first-ever All Star selection of his career. In the second half Vargas struggled, posting a 2–8 record, including a four-game losing streak. He rebounded, however, winning four straight decisions in the month of September, and in the process establishing a career-high for wins. Vargas finished the season with an 18–11 record and an ERA of 4.16 in 179.2 innings, with his 18 wins tied for the American League lead, and his 32 starts 9th in the league. He led major league pitchers in percent of balls pulled against him (48.8%). He also led all major league pitchers in changeup percentage (32.7%). On defense his 23 assists as a pitcher were 5th in the league, as his 1.60 range factor/9IP was 4th in the league and he fielded 1.000.