Pageau has played in a total of 86 Stanley Cup Playoff games, tallying 43 points (24 goals and 19 assists) and two hat tricks. During the Islanders run to the Stanley Cup semifinal in 2020-21, Pageau scored 13 points (three goals and 10 assists) in 19 games. He has 27 points (12 goals and 15 assists) in 51 career postseason games with the Islanders.
Prior to his NHL career, Pageau played 142 games in the American Hockey League with the Binghamton Senators, where he scored 94 points (38 goals and 56 assists). He also played three seasons in the Quebec Major Junior Hockey League with the Gatineau Olympiques and the Chicoutimi Saguenéens where he averaged a point-per-game, scoring 175 points (80 goals and 95 assists) in 175 games.
On the international stage, Pageau represented Canada at the 2018 IIHF Men’s World Championship, registering five points (one goal and four assists) and a +3 rating in 10 games.
Pageau was originally selected by the Senators in the fourth round (96th overall) of the 2011 NHL Draft. He was acquired by the Islanders from Ottawa in exchange for a 2020 first-round pick, a 2020 second-round pick and a 2022 third-round pick on February 24, 2020, where he signed a six-year contract with New York that same day.