Philipp Grubauer made 23 saves for the Avalanche (7-4-1), who had five games postponed due to NHL COVID-19 protocols. They were 4-0-1 in their five games prior to the postponements.
Vegas will host Colorado again Tuesday.
"We were missing our legs a bit," Avalanche coach Jared Bednar said. "We didn't have the extra pop in our legs. Our minds are in the right place, we just didn't execute the way we're capable of."
Pacioretty scored on a wrist shot from the right face-off circle for the only goal of the game at 1:38 of the second period.
Defenseman Alex Pietrangelo led the Golden Knights in ice time (25:53) alongside partner Alec Martinez (24:28). They spent most of that time defending the Avalanche's top forward line of Nathan MacKinnon, Mikko Rantanen and Brandon Saad.
Pietrangelo was on the ice for 18:16 of MacKinnon's 22:34.
"They're going to get chances, right? They're good players, they generate stuff," Pietrangelo said. "The important thing is limiting those chances. I think we did a good job, for the most part, making them defend."