On September 2, 2015, Smith re-signed with the Cavaliers. Smith played in 77 games (all starts) with Cleveland in the 2015–16 regular season, averaging 12.4 points, 2.8 rebounds and 1.1 steals in 30.7 minutes. He ranked seventh in the league in 3-pointers made (204), setting a franchise single-season record. He also shot .400 from beyond the arc, which was tied for 18th-best in the NBA. Smith led Cleveland in steal-to-turnover ratio (1.37) and scored 10 or more points 50 times and 20 or more points 11 times. During Cleveland's playoff run, Smith started in all 21 games, averaging 11.5 points, 3.2 rebounds and 1.2 steals in 34.8 minutes per game. He made a franchise playoff-record 65 3-pointers, which were also the fourth-most threes made by any NBA player in a single postseason. Smith scored in double figures in each of the last five games of the NBA Finals, as Cleveland went 4–1 over that stretch against Golden State and took home the franchise's first ever NBA title.