Selected by the Blue Jackets in the third round (No. 76) of the 2014 NHL Draft, Merzlikins played six seasons in Switzerland and was a two-time winner (2016, 2018) of the Jacques Plante Trophy, awarded to the best goalie in the National League.

Merzlikins signed a one-year, entry-level contract with the Blue Jackets on March 20, 2019 and made his NHL debut against the Pittsburgh Penguins on Oct. 5. He allowed seven goals, including five in the second period, and lost his first eight games (0-4-4).

But Merzlikins turned his season around when Joonas Korpisalo injured his knee Dec. 29; he became the sixth goalie and second rookie since 1929-30 to have five shutouts in eight games when he went 8-0-0 with a 1.00 goals-against average and .967 save percentage from Jan. 11 to Feb. 7, a stretch that included his first NHL win against the Florida Panthers on Dec. 31.

Merzlikins was 13-9-8 with a 2.35 GAA and .923 save percentage in 33 games (31 starts) when the NHL season paused March 12, 2020 due to concerns surrounding the coronavirus. He signed a two-year contract with the Blue Jackets on April 23, 2020.

Merzlikins was among the first six players selected to Team Latvia for the Olympic Winter Games Milano Cortina 2026, his Olympic debut after representing Latvia at six IIHF World Championships from 2016 to 2024. The previous season, Merzlikins made at least 30 saves 15 times, including a season-high 43 in a 5-3 win against the Detroit Red Wings at the 2025 Navy Federal Credit Union NHL Stadium Series at Ohio Stadium. A 5-1 victory against the Chicago Blackhawks on Feb. 22 was his 88th with the Blue Jackets that passed Korpisalo for third most in team history.