Luostarinen's NHL career has taken off since he was acquired by the Florida Panthers in the trade that sent Vincent Trocheck to the Carolina Hurricanes on Feb. 24, 2020.

Carolina's second-round pick (No. 42) in the 2017 NHL Draft was named to Finland's roster for the 4 Nations Face-Off during the 2024-25 season coming off a Stanley Cup championship. Luostarinen had eight points (two goals, six assists) in 24 Stanley Cup Playoff games with his 2:17 short-handed time on ice per game ranking second among Panthers forwards behind Kevin Stenlund (2:25). He had the secondary assist on Vladimir Tarasenko's second-period goal that clinched the Eastern Conference Final with a 2-1 win against the New York Rangers in Game 6.

Luostarinen played 80 regular-season games and had 19 point in all 23 playoff games to help the Panthers repeat as champions in 2024-25. He then helped Team Finland win bronze at the Olympic Winter Games Milano Cortina 2026.

Luostarinen signed a three-year contract with the Panthers on July 25, 2023, with one season remaining on a two-year contract he signed with Florida on July 8, 2022. He set what was NHL career-highs in goals (17), assists (26) and points (43) in 82 regular-season games, and had five points (two goals, three assists) in 16 playoff games including the game-winner in Game 6 of the Eastern Conference First Round against the Boston Bruins.

Luostarinen signed his entry-level contract with the Hurricanes on May 30, 2019. The Siilinjarvi native tied for second in SM-Liiga that season with seven game-winning goals and helped Finland win their first gold medal at the IIHF World Championship since 2011. He had 63 points (24 goals, 39 assists) in 141 games for KalPa from 2016-19. He also won the 2018 U20 Liiga Championship and Spengler Cup with KalPa.