Aaron Harrison was born Aaron Malik Harrison on October 28, 1994, in San Antonio, Texas to Marian and Aaron Harrison. His twin brother, Andrew, was also a member of the Wildcats roster. Aaron was one of the best clutch shooters ever at Kentucky in NCAA tournament play.
The Harrison twins began attending their father's church league basketball games at age 4. They'd climb down from the bleachers at halftime and hoist as many shots as possible. Aaron Sr. tried to sign them up for a team when they were 7, but there was only one roster spot left in their age group. So he put them in a league with sixth-graders, and the team went undefeated. The twins' most challenging games came against each other. Most summer days the thump-thump-thumping of basketballs began at 7 a.m. and continued into the night. Each basket was worth one point, and games sometimes reached 100. Most often they played until their mother, Marian, called them to come inside. Former NBA player and coach John Lucas began training the twins when they were eighth-graders. As freshmen, the Harrisons attended Strake Jesuit Prep, an all-male private school in Houston with about 800 students. Their father, who served in both the Army and the Navy, thought it would provide discipline and a demanding curriculum. The Harrisons transferred to Travis High the following year and were glad to be back home. In his junior year of high school, Harrison averaged 18.1 points, 4.7 rebounds, 2.7 assists, and 2.6 steals, leading his team to a 36-4 record and the 5A State Championship game in 2011-12. On March 9, 2012, Harrison scored 30 points behind a barrage of long 3-pointers and rim-rattling dunks, to lead Fort Bend Travis to an 85-72 win over Northside Warren in the Texas Class 5A state semifinals. He scored 19 in the first half and had eight rebounds and four assists in leading the Tigers (36-3) to the championship game in the school's first state tournament. He scored 23 points in a losing effort in the state championship game against Flower Mound Marcus on March 10, 2012. In his senior year of high school, Harrison averaged 23.1 points, 5.2 rebounds, and 2.5 assists in helping lead Travis to the state championship. On March 8, 2013, Harrison scored 19 points and grabbed 8 rebounds as Fort Bend Travis bounced back from a four-point halftime deficit to grab a 60-52 victory over Richardson Berkner in the state semifinals. On March 9, 2013, Fort Bend Travis won the state title over South Grand Prairie. Harrison, who turned his ankle in the opening seconds of the game but kept playing, scored eight points on 3 of 16 shooting. The oldest of the Harrison twins by a minute, Aaron was ranked the No. 1 shooting guard in the country by all three recruiting services, while Rivals and Scout both ranked him the fourth overall prospect in the country. ESPNU Recruiting ranked him fifth. Harrison participated in both the Jordan Brand Classic Game as well as the McDonald's High School All-America game.
On October 4, 2012, Aaron and his brother Andrew, in front of a packed gymnasium at their high school, verbally committed to play for Kentucky. They chose Kentucky over Maryland, SMU, Baylor, Kansas, and Arizona. They joined a recruiting class that was hailed as the most talented in the history of college basketball. It included Julius Randle, James Young, Dakari Johnson, Marcus Lee, and Derek Willis.
As a freshman at Kentucky, Harrison was a member of the 2013-14 NCAA Tournament runner-up Wildcats that went 29-11. He earned All-Tournament honors at the NCAA Midwest Regional and the SEC Tournament. He was twice named the league's freshman of the week. Harrison started all 40 games for UK and averaged 13.7 points, 3.0 rebounds, and 1.9 assists per game. He sank 62 3-pointers and is ranked among UK's all-time best freshman seasons in points, 3-pointers, and assists. Harrison was one of four UK freshmen named to the Wayman Tisdale Preseason watch list for the National Freshman of the Year award. On November 17, 2013, Calipari started five freshmen for the first time in UK history against Robert Morris. Harrison notched a career-high 28 points (19 in the first half), including shooting a perfect 10-for-10 from the free throw line, in Kentucky's win over Robert Morris. His three 3-pointers inside the first seven minutes got Kentucky off to a good start on it's way to an 87-49 win. Besides scoring, Harrison also flashed heads-up passing. Twice he threw fast-break lobs that teammates dunked. On November 17, 2013, Harrison scored 22 points and pulled down seven rebounds in third-ranked Kentucky's win over Eastern Michigan for the Wildcat's 500th Rupp Arena win. He was tabbed SEC Freshman of the Week for the first week of December 2013 after averaging 18.5 points, five rebounds, and three assists in wins over Eastern Michigan and Providence. On December 6, 2013, Harrison drained three 3s, scoring 15 points, while dishing out a season-best six assists vs. Baylor. He tallied 20 points in just 24 minutes of action on 8-12 shooting on the road at North Carolina on December 14, 2013. On December 21, 2013, Harrison notched more than 20 points for a second consecutive game with 23 points, six boards, and a career-high seven assists in UK's win over Belmont for his seventh consecutive game in double-figures. Harrison had begun showing signs of “an edge to him that we need everybody to have,” Coach John Calipari said. On February 1, 2014, he led UK with 21 points in a winning effort against Missouri. Harrison led UK in scoring with 21 points, four rebounds, and two steals against LSU on February 22, 2014. Harrison had been in a shooting slump before finding his stroke in the SEC Tournament. In his last four games before the tournament, he made only 11 of 43 shots. He scored another team-high 21 points at South Carolina on March 1, 2014, then led Kentucky in scoring against Georgia, knocking down four 3s to score 22 points, on March 15, 2014. Harrison scored 18 points in UK's win over K-State in the NCAA Midwest Regional Second Round on March 21, 2014, then tallied 19 points in 39 minutes as UK knocked off Wichita St in the 2013-14 NCAA Midwest Regional Third Round on March 23, 2014. Against 5th ranked Louisville on March 28, 2014, in the NCAA Midwest Regional Semifinals and in front of 41,000 spectators, he notched 15 points with three steals in UK's win, including knocking down a 3 with 39 seconds remaining to give the Wildcats a two-point lead. UK had turned up the defensive pressure. holding Louisville to just one field goal in the final 6:09, but a field goal by Russ Smith on a jumper in the lane gave U of L the lead again 68-67. That's when Julius Randle made one of the biggest plays on a night of big plays, driving and dishing to an open Aaron Harrison who calmly, smoothly sank the three. “It felt pretty good leaving my hands,” said Aaron later. When Randle sank two free throws with 13 seconds remaining all that was left was Louisville's last shot, a Smith jumper that glanced off the rim. On March 30, 2014, Harrison knocked down a 3 with 2.3 seconds to play to give UK a 75-72 edge over Michigan in the Elite Eight, his fourth 3 of the second half, sending the Wildcats to its 16th Final Four appearance. With the game tied 55-55, Aaron Harrison hit his first shot. His three-pointer with 8:05 left put the Cats ahead 58-55. A driving banker by Andrew Harrison with the shot clock inside 10 seconds put Kentucky ahead 62-55, prompting a Michigan timeout at the 6:24 mark and setting the stage for a memorable finish. Jordan Morgan's put-back tied it 72-72 with 31.6 seconds left. Tied at 72, Kentucky called timeout with 27 seconds left. Calipari joked afterward the play he drew up was deceptively simple: “Aaron, just step back and shoot a deep 3. They won't guard you.” Michigan did guard him. “I thought it was a pretty good contest,” Michigan's Caris LeVert said later. “It seemed pretty far.” — and, of course, it didn't really matter one bit. “I knew it was a big shot, but I didn't expect to get that feeling I got when it dropped,” said Harrison, a piece of nylon from the net threaded through the opening of the hat he was wearing backward. “All our tournament games have been tough games against tough teams and we've found a way to pull through. That's what tough teams do.” Harrison's game-winning 3-pointer against Michigan – a shot that may never be forgotten by UK fans – showed how much faith the staff has in him to take and make — a shot with the game on the line. His brother Andrew fed him the pass to make the shot. Just when it looked like there was no way he could top what he had done already in the tournament, Harrison did it again in the Final Four on April 5, 2014, with a 3-pointer with 5.7 seconds to play that gave UK a 74-73 comeback win over Wisconsin and a spot in the national championship game against Connecticut. Harrison took a pass from his twin brother, Andrew, spotted up from NBA range and watched the ball rattle in for the lead. “You can't be scared to miss, and you want to be that guy that wants to take the big shots,” Aaron Harrison said. It's the third game the Kentucky freshman has made a 3 for the go-ahead points in a magical ride for the 29-10 Wildcats, and the second straight time the pass has come from his brother for a shot from the left center of the arc. “We fight so hard and we never stop. We always thought we were going to win the game,” Aaron Harrison said. “Coach (John Calipari) said he wanted me to take the shot. “That gave me a lot of confidence and my teammates had confidence in me.” Of course, Harrison will forever be identified with the end of that season. Making the deciding shot in three straight games, especially three straight games deep in an NCAA Tournament, tends to immortalize a player.
Harrison returned for his sophomore season along with his brother and the core of last season's squad and were the preseason pick to win it all by most publications. Sophomore guard Dominique Hawkins won Most Surprising Revelation at the University of Kentucky basketball media day for his answer to the question: Who's your funniest teammate? “I'll say the twins,” Hawkins said, referring to Andrew and Aaron Harrison. ‘They got some good jokes. I'm pretty sure if you ask them, they'll crack a joke.” Winner of Least Surprising Thing from media day: No, they would not. But Hawkins swore both twins do a killer impersonation of Wildcats coach John Calipari when he's mad. Hawkins realizes you'll find this hard to believe. “People always talk about their body language,” he said, “but they're probably the friendliest guys off the court — and the funniest to me.” The emergence of the Harrisons' personality is indicative of how much more relaxed they were heading into their second season at Kentucky. Known for quiet-talking and mean-mugging their way through a turbulent freshman season, both said they're happier. Prior to the start of the 2014–15 season, Harrison was named the preseason SEC Player of the Year. As a sophomore, Harrison earned SEC All-Tournament Team honors after averaging 12.0 points and connecting on 6 of 11 3-point attempts in the league tournament. He played in all 39 games in 2014-15, starting all but one of them, and was named to the All-SEC Second Team by both the league's coaches and the Associated Press. Harrison averaged a team-high 11.9 points in SEC play and was UK's leading scorer in 2014-15 at 11.0 points per game. He scored in double figures a team-high 24 times and notched a team-high-tying eight games of 15 points or more. Harrison finished his two-year career ranked 22nd on UK's all-time 3-point field goals made list. He led the team in 3-point field goals made (59) and matched his career high with 43 steals, which was second on the team. Harrison made three or more 3-point field goals in a game seven times and recorded six games of three steals or more. He scored in double figures in six of Kentucky's eight postseason games. On November 21, 2014, Harrison dished out four assists in addition to 19 points in a victory over Boston. Harrison went off for a season-high 26 points in the SEC opener against Ole Miss, sinking the two game-clinching free throws in overtime, on January 6, 2015. He averaged a team-high 13.4 points in the first eight SEC games of the season, only once failing to score in 10 or more. Harrison scored in double figures in 10 of 12 games from December 10, 2014, to January 31, 2015. On January 20, 2015, with Kentucky's slim lead threatened by a Vanderbilt squad that wouldn't go away, Harrison coolly stepped up to drain a clutch 3-pointer that had become a familiar sight for the top-ranked Wildcats. Twin brother Andrew Harrison provided a little more cushion with a layup a minute later before Aaron sealed a hard-fought 65-57 victory with two free throws that kept the Wildcats perfect. “He's as good as any player in the country the way he played in the second half,” Kentucky coach John Calipari said of Harrison, his sophomore guard, whom he hugged tight after the tense contest. On February 7, 2015, he poured in a game-high 23 points, including three 3-pointers and perfect 8-for-8 performance at the free-throw line, in a come-from-behind win at Florida. On March 10, 2015, following an unprecedented undefeated regular season and the 46th Southeastern Conference championship in program history, Harrison was named to the All-SEC second team. Harrison was UK's leading scorer at 11.2 points per game and reached double-figure scoring in 18 games this season. This was the first All-SEC honor of Harrison's career. Harrison dished out a season-high six assists to go along with 11 points against No. 21 Arkansas in the SEC Tournament championship on March 15, 2015. He followed that, on March 28, 2015, with a crucial 3-pointer, his only one of the game, to give UK a lead vs. the Fighting Irish in the Midwest Regional finals. He also threw down a dunk with UK trailing by five points late in the victory over No. 8 Notre Dame. That win made Kentucky the first undefeated team to reach the Final Four since UNLV in 1991. Harrison posted 12 points on 5-of-10 shooting against Wisconsin in the 2015 NCAA Final Four. The Cats lost that one, 71-64. The 2014-15 Wildcats finished the season 38-1.
On April 9, 2015, Aaron Harrison declared for the NBA draft, forgoing his final two years of college eligibility. He was joined by his twin brother Andrew and fellow Kentucky teammates Karl-Anthony Towns, Willie Cauley-Stein, Trey Lyles, Devin Booker, and Dakari Johnson.
After going undrafted in the 2015 NBA draft, Harrison joined the Charlotte Hornets for the 2015 NBA Summer League. On July 14, 2015, he signed with the Hornets and made his NBA debut on November 20, 2015.