On 15 June 2019, Määttä was traded to the Chicago Blackhawks in exchange for Dominik Kahun and a 2019 fifth-round draft pick. In the 2019–20 season, he tallied four goals and 17 points in 65 games with the Blackhawks, while averaging 18:25 time on ice. In nine post-season games, he led the team with a plus-seven rating and paced the blueline in scoring with three goals and six points.