Ellis, a 6-foot-2 guard out of Mission Bay High School (San Diego), chose the Blue Devils from a final five that also included Memphis, North Carolina, San Diego State and USC.
"Coach [Mike Krzyzewski] had the best vision for me," Ellis told ESPN. "He really put out a plan for me to help me succeed, and it really gave me the best vision out of all the schools."
Duke joined Ellis' recruitment fairly late in the process, watching him briefly in July at the Nike Peach Jam, but not offering him until September. By that time, Ellis already had cut his list to eight schools, with Duke not included. But Ellis made an exception for Duke -- and North Carolina, which also offered in September. The Blue Devils had missed on a few perimeter targets late in the summer, and Ellis quickly moved to the top of their board among backcourt prospects.
He took an official visit to Duke two weekends ago.
"Just to really come in and have the opportunity to play right away and, looking at the guard spots, wasn't too many guards on the roster," Ellis said about Duke's pitch. "The opportunity to come and play right away and be an impact player."
Duke expects to lose potential top-five NBA draft picks RJ Barrett, Zion Williamson and Cam Reddish after this season, while five-star point guard Tre Jones got off to a strong start in the Blue Devils' 118-84 blowout of Kentucky at the Champions Classic.
"I really saw the way Coach lets his players play," Ellis said of the Kentucky game. "He told me he wants me to be one of those guys. Do some of the stuff Zion and Cam are doing, scoring the ball. He wants me to come in and score. He really painted a picture, and during the game, I really saw it, the way he lets them play and get up and down the floor."
Ellis, ranked No. 40 in the ESPN 100 for the 2019 class, was one of the biggest breakout stars of the summer evaluation period, averaging 23.0 points and 5.0 rebounds for the Oakland Soldiers at the Nike Peach Jam. He shot 57.5 percent from 3-point range during the seven-game stretch.
He is Duke's second commitment in the 2019 class, joining five-star wing Wendell Moore (No. 18), who committed in early October. Krzyzewski is still in pursuit of several elite prospects, including Vernon Carey Jr. (No. 3), Isaiah Stewart (No. 4) and Matthew Hurt (No. 6).
Ellis mentioned Carey and Stewart as two guys he wants to recruit to Durham.
"I'm just there to win," he added. "I want to win games."