On January 20, 2022, in the midst of the 2021–22 season, Pachal was named captain of the Henderson Silver Knights, Vegas' new AHL affiliate.[4] Pachal made his NHL debut with Vegas on March 15, 2022.[5]
As a restricted free agent, Pachal signed a one-year contract extension with Vegas on July 28, 2022.[6] Pachal recorded his first NHL point on December 15, 2022, with a secondary assist on Reilly Smith's empty-net goal against the Chicago Blackhawks.[7] Pachal then made his NHL playoff debut on April 27, 2023, in the series-clinching Game 5 of the Golden Knights' first-round series against the Winnipeg Jets.[8][9] Vegas then went on to win the Stanley Cup Finals; despite Pachal only playing ten regular-season games and one playoff game, the Golden Knights requested an exemption to have Pachal's name engraved on the Stanley Cup alongside the rest of the team.[10]
At the conclusion of his contract, and again as a restricted free agent, Pachal signed a further two-year extension with Vegas on June 28, 2023.[11] After making the Golden Knights' opening-night roster for the 2023–24 season,[12] Pachal scored his first NHL goal on October 12, 2023, against the San Jose Sharks.[13]
After 17 games with Vegas during the 2023–24 season, Pachal was placed on waivers on February 3, 2024, and claimed by the Calgary Flames the following day.[14]