His father, Keith Tkachuk, played 1,201 games in the NHL and is a member of the United States Hockey Hall of Fame. Matthew Tkachuk's younger brother, Brady, plays with the Ottawa Senators and won bronze with the United States at the 2018 World Junior Ice Hockey Championships. Tkachuk was born in the Phoenix suburb of Scottsdale during his father's stint with the Coyotes, and grew up in the St. Louis suburb of Chesterfield, when his father was dealt to the St. Louis Blues in 2001. He attended Chaminade College Preparatory School from sixth to ninth until he decided to join the United States Hockey League. While at Chaminade, Tkachuk was in the same gym class as Boston Celtics forward Jayson Tatum.