Howard began his high school career at Perry High School in Gilbert, Arizona. As a freshman, he started in the backcourt with his brother and averaged 23 points per game, leading his team to the state semifinals. He committed to Arizona State following his freshman season. After a sophomore season where he averaged 32.4 points per game, Howard decommitted from Arizona State and reopened up his recruitment. For his junior season, Howard transferred to national basketball power Findlay Prep in Henderson, Nevada. During his junior season at Findlay Prep, where he led the team in scoring, Howard announced that he would reclassify to the class of 2016 and signed with Marquette.
College career
As a freshman, Howard entered the starting lineup and averaged 13.2 points per game and led the country in three-point shooting at 54.7%. He was named to the 2017 Big East Conference All-Freshman team. As a sophomore, Howard became one of college basketball's top scorers. On the season, Howard averaged 20.4 points per game and was named second-team All-Big East. He also finished the season with the NCAA’s second-best free throw percentage. Going into his junior season of 2018–19, Howard earned national preseason recognition, appearing on the watch lists for the Wooden Award, the Naismith Award and the Bob Cousy Award for top point guard. Howard was also selected preseason first-team All-Big East. In Marquette’s non-conference schedule, Howard recorded two 45-point games, against ranked teams Kansas State and Buffalo. In the Buffalo win, Howard scored 40 of his total in the second half. He scored a career-high 53 points in an overtime win over Creighton on January 9, 2019, breaking a Big East single-game record. Howard became Marquette's all-time leading scorer when he contributed 38 points in an 88–53 victory against Loyola in the team’s season opener of his senior year. He was named Big East player of the week on November 11, 2019. On November 29, Howard scored 51 points in a 101–79 win over USC. He became the third player to score 50 points in a game in three straight seasons, joining Wayman Tisdale and Pete Maravich. In addition, since he scored 40 points in the previous match, he joined Maravich, Johnny Neumann, and Bob Pettit as the only players in major conferences to score 40 points on back-to-back days. Howard sat out a game against Jacksonville on December 4 with a concussion. On February 12, 2020, Howard scored 24 points and had five rebounds and two assists in a 72–71 loss to Villanova. He became the Big East's all-time leading scorer in league games, surpassing Lawrence Moten's 1,405 points. At the conclusion of the regular season, Howard was unanimously selected to the First Team All-Big East. Howard averaged 27.8 points and 3.3 assists per game as a senior.
Howard's older brother Jordan Howard played college basketball for Central Arkansas and was the 2018 Southland Conference Player of the Year. The brothers were teammates for one season at Perry High. He is of Puerto Rican descent. Howard is very public about his Christian faith. Howard explained the reason why he wears number 0 by saying, “First and foremost, I’m a Christian before anything else. I’m a son , so I want to be sure that my number meant something and it represented something. It truly represents that without my relationship with Christ, I feel like I am not the person that I’m meant to be.“ In 2018, Howard started a Fellowship of Christian Athletes club at Marquette.
