Reilly Smith tied it 1-1 on the power play at 4:04 of the second period. He had gone eight games without a point.
Tomas Nosek gave the Golden Knights a 2-1 lead at 16:28 with his second goal in five games. Nicolas Hague scored 1:26 later to make it 3-1 at 17:54.
"I thought we had a good start, and then they obviously started playing better and we didn't quite match it," Kings captain Anze Kopitar said. "I thought our first period was good, and part of the second was not terrible. Not great, but not terrible, which just isn't good enough."
Alec Martinez scored his first goal against his former team at 12:35 of the third period for the 4-1 final. The defenseman was acquired by Vegas in a trade with Los Angeles on Feb. 19, 2020.
"It was nice," Martinez said. "Obviously a good feeling, but I was more concerned with trying to close it out in the third. On a personal level, it's cool, but more concerned on the team side of it, trying to put another nail in the coffin."
NOTES:Kings forward Trevor Moore played his 100th NHL game. … Oscar Dansk backed up Lehner because Marc-Andre Fleury was given the night off. … Nosek has scored seven points (two goals, five assists) in his past seven games. … It is the Golden Knights' sixth streak of at least six consecutive home wins during their four-year history. Their record is eight straight, set in 2017-18. … Vegas forward Mark Stone had an assist, giving him 23 points (eight goals, 15 assists) in 14 games in March, tied with Edmonton Oilers forward Connor McDavid (seven goals, 16 assists, 13 games) for the most in the NHL. … Los Angeles had killed 20 consecutive penalties over nine games before Smith's goal. … Vegas forward Cody Glass had one shot on goal and two blocked shots in 14:30 after being a healthy scratch the previous three games.