Playing alongside his father Michael Nylander with Södertälje SK, he earned an assist in his first professional game on a goal by Robert Carlsson.

[2] Nylander closed out his 2013–14 season with a successful 22-game rookie stint in the Swedish Hockey League (SHL), where he would play as many as 20 minutes per night.

[3] Ranked as a top prospect in the 2014 NHL entry draft, he was ultimately selected eighth overall by the Toronto Maple Leafs.

[4][5] Nylander was highly praised for his offensive talent and puck-moving abilities; however, criticisms were drawn to his defensive game and then-small stature, measuring 5 feet 9 inches (175 cm) tall and weighing 169 pounds (77 kg; 12 st 1 lb) at the draft combine.

[8] Nylander experienced a sensational campaign despite joining the AHL squad mid-season, scoring 32 points in 37 games playing on the right-wing.

He was vital in helping the Marlies, who were at the bottom of the standings prior to Nylander joining, reach the 2015 Calder Cup playoffs.

He debuted alongside Zach Hyman and Auston Matthews on 12 October 2016, in the season opener against the Ottawa Senators.

[15] Nylander's 61 points helped the Maple Leafs qualify for the 2017 Stanley Cup playoffs, where they were eliminated in six games by the Washington Capitals.

[26] Nylander was a healthy scratch for his first game back with the team, but made his season debut on 6 December, against the Detroit Red Wings.

[28] Nylander's play markedly improved the following season, especially following the Maple Leafs' decision to replace Mike Babcock as head coach with Sheldon Keefe.

[31] He spent the majority of his youth in the United States where his father played for several NHL teams, spending the summers in Sweden.

Nylander's younger brother Alexander, who was selected eighth overall by the Buffalo Sabres in the 2016 NHL entry draft,[36] also plays for the Toronto Maple Leafs.