Pachal signed a two-year contract with the Flames on Tuesday worth $1,187,500 annually, according to Pat Steinberg of Sportsnet 960 The Fan.
Pachal scored a goal in Tuesday's 4-3 win over the Predators.
Pachal notched an assist in Saturday's 4-2 loss to the Canucks.
Pachal recorded an assist and five hits in Saturday's 6-3 win over the Oilers.
Pachal was claimed off waivers by the Flames on Sunday, Chris Johnston of The Athletic reports.
Pachal was put on waivers Saturday, according to Elliotte Friedman of Sportsnet.
Pachal has played in just four games since the start of December.
Pachal has played in just two of the Golden Knights' 10 games in December.
Pachal, who was eligible to become a restricted free agent Saturday, inked a two-year, $1.55 million contract with Vegas on Wednesday.
Pachal was summoned from AHL Henderson on Saturday, according to CapFriendly.