Lee appeared in 49 games for the Warriors during the 2019-20 season. He saw 29.0 minutes per game and set career highs with 12.7 points, 4.9 rebounds and 2.7 assists per game, plus 87.3 percent free-throw shooting. He also swiped 1.0 steals per game and shot 41.7 percent from the field and 35.6 percent from three on 4.9 attempts. Lee set new single-game career marks of 26 points, 15 rebounds and eight assists. His best overall performance of the season occurred during his 15-rebound effort, which was against the Rockets on Christmas Day. Lee also accumulated 22 points (5-9 FG, 2-2 3Pt, 10-10 FT), four assists and three steals in 31 minutes. It was one of Lee's three double-doubles. Each month from December onward, Lee averaged at least 30 minutes per game. He had two separate eight-game streaks of scoring in double-digits. The first was from Dec. 20 through Jan. 4, and Lee averaged 16.8 points on 11.9 shots, 8.0 rebounds, 2.4 assists and 1.3 steals in 32.9 minutes. The second was from Feb. 10 through Mar. 1, with Lee averaging 16.3 points on 12.1 shots, 4.6 rebounds, 3.6 assists and 1.3 steals in 32.5 minutes.

In 2018-19, Damion Lee played 32 games for the Golden State Warriors and 24 games for the G League Santa Cruz Warriors. During his sophomore season at the NBA level, the 26-year-old averaged 4.9 points and 2.0 rebounds in 12 minutes per game. Lee shot 44 percent from the field, including 40 percent from behind the arc, where he hit 27-of-68 attempts. Lee also shot 86 percent from the free-throw line, hitting 19-of-22 attempts. On March 2, Lee shot a season-best 4-of-5 from long range and finished with 12 points in a road win over the 76ers. Lee had his best game of the season April 9, tallying a season-high 20 points on 7-of-13 shooting, including 4-of-7 from beyond the arc, along with seven rebounds, an assist and a steal in a win at New Orleans. The 6-foot-6 wing scored in double digits a total of five times over his 32 appearances. Lee tallied 158 points in a total of 375 minutes played during the season. While with Santa Cruz, Lee delivered 20.3 points, 6.0 rebounds and 1.3 steals per G League contest. Lee's two-way contract with the Warriors will expire at the start of the new league year.

During the 2017-18 season, Lee played 15 games for the Atlanta Hawks and 38 games in the G-League with the Santa Cruz Warriors. The season marked the 25-year-old's NBA debut. Lee opened the year in Santa Cruz. On Nov. 10, he opened the G-League season with eight points, two rebounds, an assist and a steal. Seven days later, Lee caught fire, beginning a streak of scoring in double digits for 15 straight G-League games. During a Dec 22. loss to Reno, Lee produced 14 points, 10 rebounds and four steals. He generated another double-double five games later in a win over Greensboro. On March 10, Lee played his last G-League game of the year and delivered 25 points, eight rebounds, seven assists and two steals in a win over the Memphis Hustle. On March 12, Lee signed a 10-day contract with the Atlanta Hawks. The 6-foot-6 guard averaged 10.7 points, 4.7 rebounds and 1.9 assists over 15 contests for the Hawks.