Dejan Joveljic, Joseph Paintsil and Miguel Berry also scored for the Galaxy (8-3-7), who moved to third in the Western Conference standings, three points behind first-place Real Salt Lake. The win also kept them unbeaten through eight home games for the first time since 2016.
Only two other MLS teams — the New York Red Bulls and LAFC — have yet to lose at home this season, while the four goals matched a season high for the Galaxy.
“Home games are huge,” midfielder Diego Fagundez said. “That’s the key part, making sure that when we come home, we make it hard for teams. And we are doing that.
“We’re scoring a lot of goals, but at the same time, we need to be a little bit better defensively. It would be nice to win a game 2-0 or 1-0. I keep saying it over and over: If this team plays 90 minutes, I don’t think there’s a team that’s better than us.”
The Galaxy, returning after a two-week break and playing without playmaker Riqui Puig, who is nursing a groin injury, went ahead to stay on Joveljic’s goal in the 40th minute. After a tedious start in which the teams combined for only two shots on goal, the Galaxy got three in a matter of seconds, the final a right-footed shot from Joveljic that found the back of the net.
The sequence started with Pec putting a right-footed shot on goal from just inside the box. Kansas City keeper Tim Melia parried that away with both hands, but the ball dropped at the feet of Joveljic, who redirected it on goal. This time Melia made the save with his body as he went to the turf and the rebound hit Joveljic in the chest, allowing him to gain control and dribble past the keeper before sending a shot into the roof of the net from a right angle.
The goal was Joveljic’s team-leading 10th of the season.
Pec, who had a massive game, then doubled the lead nine minutes into the second half, running on to a chipped pass from Joveljic, dribbling into the center of the box and driving a low left-footed shot across his body and just inside the near post.
The goal was Pec’s fifth of the season, the assist Joveljic’s third.
Sporting Kansas City scored in the 66th minute when Stephen Afrifa came off the bench to one-time a left-footed shot past a sprawling John McCarthy just seconds after entering the game. But Paintsil restored the two-goal lead nine minutes later on a breakaway tally.
Defender Miki Yamane set up the goal with a long diagonal ball to Pec. Two Kansas City defenders collapsed on him, leaving Paintsil, playing for the first time in a month, open in the center of the box. Pec pushed the ball to him and the easy finish gave Paintsil his fifth goal of the season.
“It was great to get Joe back,” Galaxy coach Greg Vanney said of Paintsil, who came on at halftime. “He’s got to get back into match fitness and just get sharp again. He probably had three chances to score. He could have had a hat trick in 30 minutes.
“He does so many things at a high speed [so] repeatability is something you’ve got to work [on]. It doesn’t just come overnight.”
But Kansas City (3-10-5), which has won only one of its last 12 games, wouldn’t quit, pulling to within a goal again in the 82nd minute when defender Robert Castellanos bounced a shot off McCarthy’s outstretched right hand and in at the near post.
That was as close as Kansas City would get, though, with Berry closing the scoring for the Galaxy two minutes into stoppage time, sliding to redirect a Pec pass in with his right foot. The two-assist game was the first for Pec in MLS.