Hintz impressed in 2017-18, his first season in North America, but the Dallas Stars held off on promoting him from Texas of the American Hockey League. The forward used that full season in the minors to make important strides on the way to becoming an NHL regular.
Hintz scored 35 points (20 goals, 15 assists) in 70 games that season for Texas, then had 14 points (four goals, eight assists) in 22 playoff games to help Texas reach the Calder Cup Finals, where it lost to Toronto in seven games.
That performance led to Hintz making Dallas' 2018-19 opening night roster. After being sent down later in October, he scored his first NHL goal Nov. 18, 2018, at the New York Islanders one day after being recalled. He played 58 games as a rookie in 2018-19.
Among Stars forwards, he tied Devin Shore for third with three game-winning goals and was fourth with three power-play goals. Hintz then scored five goals in 13 Stanley Cup Playoff games, tying forward Alexander Radulov for the team lead. Hintz followed that by scoring 19 goals and 33 points in 60 games in 2019-20 and 13 points (two goals, 11 assists) in 25 postseason games, helping the Stars reach the Stanley Cup Final for the first time since 2000.
The Stars selected Hintz in the second round (No. 49) of the 2015 NHL Draft. He signed a three-year, entry-level contract with Dallas on May 4, 2017, after scoring 30 points (11 goals, 19 assists) in 44 games in 2016-17 for HIFK in Liiga, the top professional league in his native Finland.
Hintz made his Liiga debut playing with Ilves during the 2013–14 Liiga season. On 23 April 2015, after two seasons with Ilves, Hintz transferred to fellow Liiga club HIFK on a two-year contract. Hintz was ranked by NHL central scouting amongst the eligible European skaters before his selection by the Dallas Stars in the 2015 NHL Entry Draft.