Wiggins was born in Toronto, Ontario and raised in the nearby Thornhill neighbourhood of Vaughan, Ontario. He is the son of former NBA player Mitchell Wiggins, an American, and former Olympic track and field sprinter Marita Payne-Wiggins, a Canadian who is originally from Barbados. His parents met as student-athletes at Florida State University. He attended elementary school at Glen Shields Public School in Vaughan.
Wiggins has two older brothers. His middle brother, Nick, played college basketball at Wichita State University and his oldest brother, Mitchell Jr., played at Hillsborough Community College and Southeastern University. He also has three sisters: Stephanie, Angelica, and Taya.
Wiggins attended Vaughan Secondary School in Vaughan for his first two years of high school. In his 2010–11 sophomore year, he led the school's senior basketball team to a 44–1 record, en route to winning the Ontario provincial championship. In the championship game, he scored 25 points and grabbed 13 rebounds, amid chants of "Over-rated!" from the crowd.
In 2011, he transferred to Huntington Prep School in Huntington, West Virginia. During his junior season, he averaged 24.2 points, 8.5 rebounds, 4.1 assists and 2.7 blocks per game. As a senior, he averaged 23.4 points, 11.2 rebounds, 2.6 blocks and 2.5 assists per game.
Wiggins had been rated as the top prospect for 2014, but announced in October 2012 that he would officially reclassify into his original high school class of 2013, and was immediately placed ahead of the previous number one prospect, Jabari Parker, by ESPN.
On February 7, 2013, after an article in Sports Illustrated criticized Canadian basketball and Wiggins' work ethic, he responded later that day, scoring 57 points in a 111–59 win over Marietta College.
Wiggins was named the 2013 Naismith Prep Player of the Year on February 25. He was named the 2013 Gatorade National Player of the Year on March 28 as the nation's top high school player. He was the first Canadian player to be so named. In May 2013, he was named Mr. Basketball USA. He was ranked number one high school basketball player by SLAM Magazine.
In April 2013, Wiggins played in the Jordan Brand Classic All-American game in Brooklyn. He scored 19 points and tied Julius Randle for lead scorer for the East team.
Wiggins committed to Kansas on May 14, 2013. Before the announcement, he had narrowed his choices to Florida State, Kentucky, Kansas and North Carolina. Wiggins joined the Kansas team on June 19, 2013.
On January 13, 2014, Wiggins scored 17 points and collected 19 rebounds in a 77–70 victory over Iowa State, becoming only the second freshman in the last 15 years (along with Michael Kidd-Gilchrist) to amass those numbers in a win against a ranked opponent.
Wiggins averaged 17.1 points per game (ppg), 5.9 rebounds per game (rpg), and made 34.1% of his three-pointers in his freshman year at Kansas. On January 22, 2014, Wiggins was named a Top 25 Finalist for the John R. Wooden Men's Player of the Year award by the Los Angeles Athletic Club. On February 28, he was named one of the 10 semi-finalists for Naismith College Player of the Year.
On March 8, 2014, Wiggins scored 41 points against West Virginia, the most for a Big 12 Conference freshman since Michael Beasley scored 44 points against Baylor in 2008.
Wiggins declared for the 2014 NBA draft on March 31, 2014. He was selected first overall in the draft by the Cleveland Cavaliers on June 26, 2014, becoming just the second Canadian ever picked number one in the draft, after Anthony Bennett, who had been selected first overall one year prior in the 2013 NBA draft, also by Cleveland. On July 24, Wiggins signed his rookie scale contract with the Cavaliers. On August 23, a three-team trade was completed involving the Cavaliers, the Minnesota Timberwolves, and the Philadelphia 76ers. As part of the deal, Wiggins and teammate Anthony Bennett were traded to the Wolves, along with Thaddeus Young, then of the Sixers. The Cavaliers received Kevin Love from Minnesota, whereas the Sixers received Luc Mbah a Moute and Alexey Shved from Minnesota and a 2015 first round draft pick from Cleveland. Wiggins became just the second player since the ABA–NBA merger to be drafted as the number one pick, only to be traded afterwards without playing a single game for the team he was originally selected for; Chris Webber was the first following the 1993 NBA draft.
On October 29, 2014, Wiggins made his NBA debut in the Timberwolves' season opener against the Memphis Grizzlies. In 18 minutes of action as a starter, he recorded 6 points, 3 rebounds, 2 steals and 1 assist in the 105–101 loss. He went on to earn the Western Conference Rookie of the Month for games played in October and November 2014. Wiggins won the Western Conference Rookie of the Month for December as well after averaging 14.6 points and 4.1 rebounds per game. On January 31, 2015, he had a season-best game with 33 points on 14-of-25 shooting and 4 steals in a loss to the Cleveland Cavaliers. On February 13, Wiggins won the Rising Stars Challenge MVP after scoring 22 points for Team World in a 121–112 win over Team United States. On April 30, he was named the Rookie of the Year for the 2014–15 season.
On October 21, 2015, the Timberwolves exercised their third-year team option on Wiggins' rookie scale contract, extending the contract through the 2016–17 season. On November 7, 2015, he scored a game-high 31 points in a 102–93 overtime win over the Chicago Bulls. Two days later, he tied his career-high of 33 points in a 117–107 win over the Atlanta Hawks, marking the first time scoring back-to-back 30-point games in his career. On December 18, he recorded 32 points, 10 rebounds and six assists in a 99–95 win over the Sacramento Kings, joining LeBron James, Kevin Durant and Tobias Harris as the only players 20 or younger to record at least 30 points, 10 boards and five assists in a game since 2000.
Wiggins participated in the 2010 FIBA Under-17 World Championship and 2012 FIBA Americas Under-18 Championship, helping the Canadian junior national team win a bronze medal in each tournament. During the 2010 tournament, Wiggins was a teammate of Anthony Bennett, the number one overall pick in the 2013 NBA draft and his former teammate on the Timberwolves. In the 2012 tournament, he led the team in scoring with 15.2 ppg, along with 7.6 rpg.
On August 20, 2015, Wiggins was named on the Canadian national team roster for the 2015 FIBA Americas Championship, a qualifying tournament for the 2016 Summer Olympics. Wiggins helped Canada win the bronze medal; he led the team in scoring with 15.1 ppg and was named on the tournament's All-Star Five team.
After being drafted, Wiggins signed an endorsement deal with Adidas that, at the time, was one of the most lucrative endorsement deals ever given to an NBA rookie. Wiggins primarily wore the Adidas Crazlight Boost basketball shoe during his rookie season.