As a junior, Edwards saw his efficiency dip from 46.8% (40.6% from 3) to 39.4%, and 35.5% from 3. However, he also took about 19 shots per game as opposed to around 13.5 during his sophomore season. This was also due to a shooting slump in February 2019 where he shot around 30% from the floor.
Edwards broke many records in the 2019 NCAA tournament. He broke the single-tournament 3-point record with 28. However, the previous record holder had played in all six games to Edwards' four. He is also all-time 3rd place in most 25-point games in a row in the NCAA tournament, tying current NBA player Stephen Curry with 5.
Following Purdue's loss in the 2019 NCAA Men's Basketball Tournament, Edwards announced his intention to forgo his final season of collegiate eligibility and declare for the 2019 NBA Draft, where he was projected to be a first-round selection.
On June 20, 2019, Edwards was selected with the 33rd overall pick in the 2019 NBA draft by the Boston Celtics after his draft rights were traded by the Philadelphia 76ers. Edwards played for the Celtics during the 2019 NBA Summer League season and averaged a team high 19.4 points, 3.8 rebounds, and 1.4 assists in 23.4 minutes over five games. After clinching the number one seed in the tournament, the Celtics were eliminated in the first round by the eventual champions, the Memphis Grizzlies, despite a 25 point, 8 rebound effort by Edwards. On July 14, 2019, the Celtics announced that they had signed Edwards. On October 23, 2019, Edwards made his debut in NBA, coming off from bench in a 93–107 loss to the Philadelphia 76ers with three points and a rebound. Edwards scored a career high 18 points in a 140–133 win against the Washington Wizards on November 13. Edwards finished with eighteen points, four rebounds, three assists, and a steal in 20 minutes.
