[7] Tavares showed such promise as a hockey player that when he was seven, his parents moved him up one age group and he began playing with older children.

[12] For his achievements, Tavares shared the Buck Houle Award with Bryan Cameron, "in recognition of outstanding on ice performance, leadership and loyalty".

[13] During this season, he also played 16 games with the Milton Icehawks of the Ontario Provincial Junior A Hockey League (OPJHL), during which he recorded 11 goals and 23 points.

[34] In October 2007, it was reported that then-Toronto Maple Leafs general manager John Ferguson Jr. had offered the 17-year-old Tavares a spot with the team's American Hockey League (AHL) affiliate, the Toronto Marlies.

[35] The NHL International Scouting Services ranked Tavares as the top draft prospect in the world, ahead of defenceman Victor Hedman and forwards Magnus Pääjärvi-Svensson and Matt Duchene in its March 2009 update.

[42] At the end of the season, Tavares finished second in rookie scoring, behind Colorado Avalanche forward Matt Duchene, with 54 points (24 goals, 30 assists) in all 82 games played.

[52] Additionally, Tavares was named a finalist for the Hart Memorial Trophy for the second time in his career; ultimately ceding the award to Montreal Canadiens goaltender Carey Price.

On April 19, 2015, Tavares scored 15 seconds into overtime against Washington Capitals goaltender Braden Holtby in Game 3 of the Eastern Conference Quarterfinals of the 2015 playoffs.

He finished the job by scoring the series-clinching goal in double overtime, winning a playoff series for the Islanders for the first time since 1993 before getting ousted in the second round in five games by the Tampa Bay Lightning.

[61][62] Just before 1 pm, almost one hour into the free agency period, it became public knowledge that Tavares had informed the Islanders he would be leaving the team and signing with Toronto.

[64] Tavares cited "Toronto's chances as a Stanley Cup contender, as well as living out his childhood dream to play for his hometown team", as his reason for signing the contract.

[65] In his debut for the Maple Leafs in the 2018–19 season opener on October 4, 2018, against the Montreal Canadiens, Tavares scored his first goal for the club on goaltender Carey Price in a 3–2 overtime win.

[73] In so doing, he became just the third player in modern team history (since 1943) to record multiple hat-tricks in his debut season with the club, following Wilf Paiement and Daniel Marois.

In the opening round of the 2019 playoffs, the Maple Leafs would be eliminated in seven games by the third-seeded Boston Bruins for the second consecutive year and surrendering a 3–2 series lead this time around.

Prior to the 2019–20 season, Tavares was granted a leave of absence from the team's first pre-season game in St. John's, Newfoundland and Labrador in September 2019 to spend with his wife and newborn son.

[77] On October 2, 2019, just before the first game of the NHL season against the Ottawa Senators, Tavares was named the 25th captain in the history of the Maple Leafs,[78][79] filling a position that had been vacant for more than 3+1⁄2 years since the trade of Dion Phaneuf.

Forbes remarked on the occasion that "in terms of individual achievements, the 32-year-old has absolutely realized the lofty potential that made him the first-overall pick in the 2009 NHL draft.

While the Leafs were generally identified as the favourites going into the series as the higher seeded team, the long history of failure to advance past the first round was widely acknowledged.

[91] He would go on to score the series-winning goal against Lightning goaltender Andrei Vasilevskiy in overtime in Game 6, sending the Maple Leafs to the second round for the first time since 2004.

His 1,000th point came from an assist on a game-tying goal by Morgan Rielly with 6.4 seconds left in the third period to send the game to overtime, which the Maple Leafs ultimately lost 4–3.

[93] The Islanders organization offered a congratulatory tribute to Tavares on the jumbotron prior to the overtime period, which was largely booed by the home New York fans in attendance.

Later in the off-season, he was invited to the under-18 team's summer training camp to prepare for the 2006 Ivan Hlinka Memorial Tournament in the Czech Republic and Slovakia, though an injury ultimately prevented him from participating.

Tavares earned another invite to the selection camp for the 2008 World Junior Championships and made the final roster for the tournament on his second attempt.

[100] In the final round-robin game against the United States, Tavares scored a hat-trick for his 12th career goal of the tournament to tie Eric Lindros and Jeff Carter for the all-time Canadian junior record.

[102] Meeting Russia in the semifinal and down 5–4 with less than ten seconds left in regulation, Tavares fought off two Russian players along the boards and backhanded a shot towards the goal.

[104] As the New York Islanders failed to qualify for the playoffs in Tavares' rookie season in the NHL, he was selected to the Canadian men's team for the 2010 IIHF World Championship in Germany.

Canada General Manager Mark Messier made a specific effort to assemble a young team;[105] as a result, Tavares was one of five teenagers on the final roster.

He improved to nine points over seven games with five goals and four assists to lead Canada in scoring; he ranked fifth among all tournament players for the second consecutive year.

[113] After the Maple Leafs were eliminated from the 2019 Stanley Cup playoffs by the Boston Bruins, Tavares committed to play for Team Canada at the 2019 IIHF World Championship in Slovakia.

[115] Following the Maple Leafs' first-round exit from the 2024 Stanley Cup playoffs, Tavares was a late addition to the Team Canada roster for the 2024 IIHF World Championship.