On July 24, 2018, Harris re-signed with the Nets. On October 19, 2018, in a 107–105 win over the New York Knicks, Harris' first three-pointer was his 237th as a Net, moving him into 10th place on the franchise's career list. On November 4, in a 122–97 win over the 76ers, Harris made a three-pointer in his 25th straight game, moving into sole possession of fourth place on the Nets' career list. On December 23, in a 111–103 win over the Phoenix Suns, Harris made 3 three-pointers, making him the first player in franchise history to make three or more in six straight games. On December 26, he scored a season-high 27 points and made a game-winning layup with 3.4 seconds left in the second overtime to lift the Nets to a 134–132 win over the Charlotte Hornets. On February 11, 2019, he scored 24 points and made a career-best 7 three-pointers in a 127–125 loss to the Toronto Raptors. On February 16, he won the Three-Point Contest during All-Star weekend. In the playoffs, he shot 4-of-21 from 3-point range over five games.