After Maxey's freshman season at Kentucky was interrupted by the COVID-19 pandemic, he elected to enter the 2020 NBA draft, where the 76ers selected him 21st overall with their first-round pick.

Maxey received limited playing time during his rookie season, making his first NBA start in a game where the 76ers could only field the league's minimum number of players.

He had previously broken his pinky finger during the AAU city championship in Garland, Texas, but chose to complete the game by only dribbling with his non-injured hand.

[5] The following season, Maxey averaged 22.5 points, 7 rebounds, 3.1 assists, and 2.3 steals per game, and South Garland made its first ever Texas state basketball tournament appearance.

[6] He contemplated leaving high school early after the 2018 season in order to enter the NBA sooner, but ultimately decided to finish his four-year South Garland career in the hopes of becoming a McDonald's All-American.

[8] In addition to graduating at the top of his class, Maxey was named First-Team All-Area, a McDonald's All-American, and was crowned Texas Mr.

[9] South Garland reached the 2019 Texas 6A Region II tournament finals, where despite 25 points from Maxey, they lost 64–53 to Klein Forest High School.

[15] Maxey made his college debut at Madison Square Garden for Kentucky's Champions Classic win over the Michigan State Spartans.

Playing the day after his 19th birthday, Maxey came off the bench to score 26 points, a school record for a freshman debut, in the Wildcats' 69–62 victory.

[20][21] On February 29, 2020, Kentucky clinched the SEC regular season championship with a 73–66 victory over the Auburn Tigers, during which Maxey scored 17 points.

[25] After collecting 8 and 11 points with limited minutes during two preseason games, head coach Doc Rivers decided that Maxey would be "one of our main bench guys" going into the 2020–21 season.

[31] With injuries to stars Joel Embiid and Ben Simmons and a number of positive COVID-19 tests on the team, the 76ers were only able to field the league-minimum eight players for their January 9 game against the Denver Nuggets.

[37] After averaging 16.9 points, 3.5 rebounds, and 4.6 assists in 35.6 minutes through the first 51 games of the season, Maxey was named to the 2022 NBA Rising Stars Challenge as a member of Team Worthy.

[46] On October 28, 2022, Maxey put up a career-high 44 points on 15-of-20 shooting from the field, including nine of his 12 attempts from three-point range in an 112–90 win over the Toronto Raptors.

[48] He became the sixth Sixer ever with 50+ points, 5+ rebounds and 5+ assists (Allen Iverson, Joel Embiid, Wilt Chamberlain, Hal Greer and Dana Barros).

[49] He also dedicated his career-high to his teammate Kelly Oubre Jr., who was struck by a car by a hit and run driver and went to the hospital the previous day.

[53] On April 4, Maxey fell one rebound short of a first career triple double, putting up 37 points, 11 assists in an important win at the Miami Heat.

[59] During his high school career, Maxey was named to the United States men's national under-19 basketball team for the 2018 FIBA Under-18 Americas Championship in Canada.

[66] During the 2017–18 college basketball season, their father Tyrone was the director of player development for Southern Methodist University, one of the schools that attempted to recruit his son.

[69] He is also one of the "Baggage Claim Boys", a loose group of star high school basketball players from the Dallas–Fort Worth metroplex who became friends during their college recruiting season.