In 2013, Raanta won the Finnish championship with Ässät and was awarded both the Lasse Oksanen Trophy for the SM-liiga's best player of regular season, as well as the Jari Kurri Trophy for the best player of the playoffs, posting a.955 save percentage.
Chicago Blackhawks
On 3 June 2013, Raanta signed a one-year, entry-level contract with the Chicago Blackhawks. He was recalled by the Blackhawks from the American Hockey League 's Rockford IceHogs on 17 November 2013, after Chicago's backup goaltender, Nikolai Khabibulin, suffered an injury in a loss against the Nashville Predators the previous night, 16 November. Raanta made his NHL debut against the Colorado Avalanche on 19 November 2013, stopping 14 of 16 shots in relief of starter Corey Crawford. On 30 December 2013, Raanta earned his first career shutout, beating the Los Angeles Kingsat home at the United Center. He stopped all 26 shots he faced, and improved to 10–1–3 on the season. Raanta was named Rookie of the Month for December 2013, going 8–1–3 with one shutout. On 12 January 2014, Raanta helped end his team's losing; the Blackhawks had previously lost three-straight games, with Crawford in goal for all three losses. Raanta played against the Edmonton Oilers as Chicago prevailed 5–3. On 27 June 2014, the Blackhawks signed Raanta to a two-year contract extension. In the 2014–15 season, on 15 November 2014, the Blackhawks announced that Raanta had been assigned to the Rockford IceHogs to make room for rookie goaltender Scott Darling. On 17 December 2014, Raanta was called up from the IceHogs and placed on the Blackhawks' roster, replacing goaltender Darling, who was himself demoted back to Rockford. However, on 22 February 2015, the Blackhawks again reassigned Raanta to the IceHogs after a 6–2 loss against the Boston Bruins, and called up Darling to take his place. Raanta was recalled on 12 April 2015 to join the Blackhawks in the playoffs, but did not dress in any more games. When the Blackhawks went on to win the Stanley Cup, Raanta was given a day with the Cup and a Stanley Cup ring; however, he did not meet the minimum games requirement to include his name on the Stanley Cup, nor had he dressed in the playoffs, as by this time he had been relegated to the Blackhawks' third-string goaltender.
New York Rangers
Unable to earn back the backup role on the Blackhawks at season's end, on 27 June 2015, Raanta was traded to the New York Rangers in exchange for Ryan Haggerty. Raanta would battle Magnus Hellberg for the backup role behind Henrik Lundqvist, Raanta eventually won the battle as Hellberg was sent to the American Hockey League. Raanta was put in net for the Rangers' 17 December game against the Minnesota Wild. However, near the end of the 1st period, Raanta took a slapshot to the head from Wild defenseman Marco Scandella, and left the game. Lundqvist was put in net the remainder of the game, and the next day Raanta was put oninjured reserve. Originally expected to be out 2–3 weeks, Raanta recovered faster than originally expected, returning to the Rangers lineup on 28 December. During Raanta's absence, the Rangers called up Magnus Hellberg to serve as Lundqvist's backup. Raanta made 25 appearances in the 2015–16 season, started 18 games, and finished with an 11–6–2 record. Raanta had a 2.24 GAA and a.919 Save Percentage along with one shutout. At the end of the season, Raanta agreed to terms on a two-year contract extension with the New York Rangers on 2 May 2016.
Arizona Coyotes
On 23 June 2017, he was traded by the Rangers along with Derek Stepan to the Arizona Coyotes for Anthony DeAngelo and the 7th overall pick in the 2017 NHL Entry Draft. In his first season with the club, Raanta posted a 21–17–6 record in 41 appearances. However, the Coyotes failed to qualify for the 2018 Stanley Cup playoffs. On 6 April 2018, the Coyotes re-signed Raanta to a three-year, $12.75 million contract extension worth $4.25 million annually.
