Laine began playing hockey at four years old and was primarily a goaltender, before permanently switching to forward as a youth at the advice of his father.

[7][8] After a dominant performance at the 2016 World Junior Ice Hockey Championships, Laine received greater attention from scouts and casual observers alike.

[12] The other scouts in McKenzie's April report, meanwhile, stated they needed to think "long and hard about their decision" to rank Matthews ahead of Laine.

[13] He was likewise awarded the Jari Kurri Trophy as playoff MVP, finishing the post-season with ten goals and five assists in 18 games.

[32] On 13 October 2016, he made his National Hockey League (NHL) debut in the Jets' season-opening game against the Carolina Hurricanes in which he scored a goal along with an assist.

[33] On 19 October, Laine registered his first career hat-trick in a 5–4 win against the Toronto Maple Leafs, becoming, at 18 years, 183 days old, the youngest player born outside North America to score at least twice in one game in NHL history.

[39] A week later, he broke the Winnipeg Jets / Atlanta Thrashers franchise record for the most goals in a single season by a rookie, previously held by Ilya Kovalchuk with 29.

[51] After struggling to score at the beginning of the 2018–19 season, putting up only five points in 12 games, Laine recorded his fifth career hat-trick during the 2018 NHL Global Series in his home country, Finland.

[53] On 24 November 2018, Laine recorded five goals in an 8–4 win over the St. Louis Blues, becoming the first person since Johan Franzén in February 2011 to accomplish that feat, and the 45th player cumulatively.

[56] Without contract as a restricted free agent, Laine traveled to Switzerland to train with SC Bern of the National League (NL).

Despite this improvement, his wrist would be injured early into the play-in round of the 2020 Stanley Cup playoffs against the Calgary Flames, whereas the Jets were eliminated in four games.

[60] On 9 February, controversy again surrounded Laine when, after multiple defensive lapses in a game versus Carolina, he was involved in a verbal altercation with an assistant coach and was subsequently benched for his actions.

[1] On 27 July 2021, Laine, a restricted free agent, accepted a qualifying offer and signed a one-year, $7.5 million contract extension with the Blue Jackets.

[64] After suffering a fractured clavicle in a game against the Toronto Maple Leafs on 14 December 2023, it was announced in January 2024 that Laine had entered the NHL/NHLPA Player Assistance Program, personally citing a need to prioritize his "mental health and well-being.

[66][67] This was later confirmed by newly hired Columbus general manager Don Waddell[68] who, in an August 2024 interview, stated that Laine "does not want to play for the Blue Jackets.

[73] Despite initial fears that he might miss significant playing time, it was subsequently announced that Laine would not require surgery, and would be sidelined for two to three months of the 2024–25 season while his knee rehabilitated.

[79] Just 10 games after making his season debut, he would suffer yet another injury, coincidentally in his return to Nationwide Arena versus the Blue Jackets on 23 December.

[84] In doing so, he became the seventh Finnish player in NHL history to reach this juncture in fewer than 500 games played, behind Jari Kurri, Teemu Selanne, Rantanen, Sebastian Aho, Esa Tikkanen, and Aleksander Barkov.

[86] In April 2015, Laine participated at the International Ice Hockey Federation (IIHF) sanctioned World U18 Championships for his country's national under-18 team.

Having an immediate scoring impact with linemates Jesse Puljujärvi and Sebastian Aho,[88] he was named to the tournament All-Star Team after registering a total of 13 points across seven games played.

[90] He followed this with a second consecutive three-point (two-goals, one-assist) effort against Germany, becoming the highest-scoring draft-age player in the tournament's history, surpassing Jaromír Jágr who at the same age registered three goals and two assists for five points in ten games at the 1990 World Ice Hockey Championships.

[95] Collectively, Laine was named the tournament's most valuable player, as well as a member of the annual All-Star team, and received the IIHF Directorate Award recognizing the best forward.