Before suffering a season-ending injury, he set numerous career highs in the 2012–13 season and was ranked first overall amongst international skaters by the NHL Central Scouting Bureau.

Following the draft, Barkov joined the Florida Panthers roster and made his NHL debut as the youngest player in the league during the 2013–14 season.

After being eliminated in the first round in back-to-back seasons, he continued to lead the Panthers in scoring en route to a third Stanley Cup playoffs showing.

Although he experienced setbacks due to injuries, Barkov surpassed Olli Jokinen and became the first player in franchise history to score 200 goals for the Panthers.

[22] He was reunited on the Panthers top line with Sean Bergenheim and Brad Boyes and the trio combined for five goals and three assists over four games to start the season.

[25] On 2 April, Barkov tallied an assist to help Jágr tie Ron Francis for fourth place on the NHL's career points list.

[45] Barkov's few penalties and generally clean play earned him a nomination for the Lady Byng Memorial Trophy as the league's most gentlemanly player.

[54] During the 2016 off-season, the Panthers made multiple moves to improve the team, including signing newly acquired Keith Yandle and Huberdeau to lengthy contracts.

[67] However, the Panthers lost top players Marchessault and Smith to the Golden Knights to cut costs and protect more defensemen from the expansion draft.

[70] After Dadonov suffered an injury in late-November, Denis Malgin was recalled from the American Hockey League to replace him on Barkov's top line.

[92] As part of his growing success, Barkov recorded his first career NHL hat-trick in a 4–3 overtime win over the Toronto Maple Leafs on 15 December.

[106][notes 1] On 18 April, for the third-straight season, Barkov was named a finalist for the Lady Byng Memorial Trophy, alongside Ryan O'Reilly of the St. Louis Blues and Sean Monahan of the Calgary Flames, respectively.

[108] Barkov was eventually named the winner of the trophy as he had accumulated only four minor penalties during the 2018–19 season, becoming only the second player in Panthers history (joining Brian Campbell in 2011–12) to receive the award.

[117] However, the line began to struggle through December and head coach Joel Quenneville replaced Bakov's linemates with Frank Vatrano and Brett Connolly in mid-December.

[121] While playing with his usual linemates on 16 January, Barkov picked up the 395th point of his career against the Los Angeles Kings to secure third place on the franchise's all-time scoring list.

[125] Following a loss to the Los Angeles Kings on 21 February, Barkov hit the 20-goal mark for the fifth straight season and he ranked second on the Panthers in scoring with 60 points.

[128] During the 2020 off-season, Barkov teamed up with fellow Finn Patrik Laine to co-host a charity golf tournament in support of the Association for Persons with Intellectual Disabilities.

"[130] Barkov entered the pandemic-shortened 2020–21 season with new linemates Anthony Duclair and Carter Verhaeghe, while Huberdeau joined Alexander Wennberg and Hörnqvist on the second line.

[143] Barkov subsequently set another franchise milestone by becoming the first Florida Panthers player to win the Selke Trophy as the best defensive forward in the NHL.

[153] A few days later, Barkov was listed as week-to-week after he suffered a lower-body injury following a knee-on-knee collision with New York Islanders defenseman Scott Mayfield.

[161] Barkov led the Panthers to the Presidents' Trophy with the league's best record as he finished the regular season with 39 goals, 49 assists and 88 points through 67 games.

[153] The Panthers struggled against the two time defending Stanley Cup champion and fifth-seeded Tampa Bay Lightning and Barkov ended their series with only one assist as they were swept in four games.

[176][177] The month of March saw the Panthers pull within a playoff position by winning three consecutive games before falling out due to a four-game losing streak.

[168] On 20 March, during a game against the Detroit Red Wings, Barkov passed former teammate Jonathan Huberdeau to become the Florida Panthers' all-time leading scorer with 614 points.

[179] Over the final eight games of the season, Barkov, Tkachuk, Reinhart, and Brandon Montour all accumulated 12 points to help the Panthers clinch the second wildcard spot in the Eastern Conference.

[180] In the second to last game of the season on 8 April, the Penguins fell to the Chicago Blackhawks, resulting in the Panthers qualifying for the playoffs by one point as the eighth and final seed in the Eastern Conference.

[172] He was also nominated by the Panthers for the King Clancy Memorial Trophy as a player who "best exemplifies leadership qualities on and off the ice and has made a noteworthy humanitarian contribution in his community."

He made his international debut with the Finland men's national junior ice hockey team during the 2011 Ivan Hlinka Memorial Tournament.

[200] As a result of his success, Barkov was invited to the 2014 Winter Olympics in Sochi to represent Finland, but suffered a knee injury after two games and was unable to continue playing in the tournament.

[3] While both Aleksander and his father played ice hockey, his older brother Juri was an aspiring professional tennis player before injuries cut his career short.