On November 12, 2018, Russell made a career-high nine 3-pointers and scored 31 points in a 120–113 loss to the Minnesota Timberwolves. On November 25, he had his highest scoring total with the Nets, recording 38 points, eight assists and eight rebounds in a 127–125 loss to the 76ers. On December 18, he had 22 points and a career high-tying 13 assists in a 115–110 win over the Los Angeles Lakers. On January 2, he had 22 points and 13 assists in a 126–121 win over the New Orleans Pelicans. On January 14, he scored 18 of his 34 points in the third quarter of the Nets' 109–102 win over the Boston Celtics. On January 18, he matched his career high with 40 points in a 117–115 win over the Orlando Magic. He was subsequently named Eastern Conference Player of the Week for games played from Monday, January 14, through Sunday, January 20. It was his first career Player of the Week award. On February 1, 2019, he received his first All-Star selection as a replacement for the injured All-Star Victor Oladipo in the 2019 game. On February 11, he recorded 28 points and a career-high 14 assists in a 127–125 loss to the Raptors. On February 13, he scored 14 of his 36 points in the third overtime of the Nets' 148–139 triple-overtime win over the Cavaliers. On February 23, he tied a career high with 40 points in a 117–115 win over the Hornets. On March 19, Russell scored 27 of his career-high 44 points in the fourth quarter, keying the Nets' 123–121 win over the Sacramento Kings after trailing by as many as 28. He also had four 3-pointers in the fourth quarter, breaking Allen Crabbe's single-season franchise record of 201 3-pointers. On March 25, he had 39 points, nine rebounds and eight assists in a 148–144 double-overtime loss to the Portland Trail Blazers.