Reilly Smith and Mark Stone also scored, and Marc-Andre Fleury made 36 saves as the Golden Knights swept their first set of back-to-back games.
Vegas was 3 for 3 on the power play after starting the season 3 for 17 with the man-advantage.
Jonathan Quick allowed five goals on 36 shots for the Kings. Quick has allowed 19 goals on 92 shots in his three appearances this season. He has allowed at least five goals in five of his last seven starts.
Stastny redirected Pacioretty’s pass between Quick’s legs to put the Golden Knights up 3-1 at 14:51 of the second period. He made it 4-1 with a one-timer on a feed from Jonathan Marchessault 2:09 later. It was Stastny’s second career game with two power-play goals, and he finished with four points.
Dustin Brown pulled the Kings within 4-2 at 4:24 of the third period, but Stone pushed the lead back to three goals by scoring 17 seconds later.
Vegas went in front 1-0 at 5:42 of the first period on Smith’s fourth goal of the season. Smith scored on a wrist shot from the left circle, with William Karlsson providing his sixth assist through five games.
Pacioretty scored on the power play at 6:59 to make it 2-0, scoring from the right dot after being given too much space by the Kings. But Los Angeles cut the deficit to 2-1 on Austin Wagner’s first goal of the season 50 seconds later.
NOTES: Fleury played in his 804th game, passing Harry Lumley and moving into 15th place in career appearances by an NHL goalie. … Vegas coach Gerard Gallant won his 250th NHL game. … Golden Knights D Shea Theodore had two assists.
Golden Knights: Host the Nashville Predators on Tuesday to open a two-game homestand.
Kings: Host the Carolina Hurricanes on Tuesday in the third game of a five-game homestand.