Another entertaining clash between these two rivals was ignited early when Chicharito opened the scoring after just 13 minutes, meeting a Samuel Grandsir ball at the far post.
Compatriot Carlos Vela hit the post and had a goal ruled out for offside shortly after, but it was the Galaxy who celebrated again when Sega Coulibaly met another beautiful Grandsir delivery.
LAFC pushed hard after half-time and finally found the net when Cristian Arango fired home the rebound as Jonathan Bond saved another Vela effort.
But it wasn't to be for the Black and Gold, who were left desperately chasing a lost cause with their unbeaten record this season finally slipping away. Latif Blessing's late equalizer ruled out following a VAR only served to sum up LAFC's poor luck on the day.
The win puts the LA Galaxy on 12 points after six games, just one adrift of LAFC who went into this weekend top of the overall standings.
Here are full player ratings from another entertaining Trafico encounter:
LA Galaxy player ratings
1. Goalkeeper & defenders
Jonathan Bond (GK) - 7 - Made a couple of big saves to keep the Galaxy out of reach.
Julian Araujo (RB) - 6 - A solid hour from Araujo, who was clean on the ball and aggressive in defense.
Sega Coulibaly (CB) - 8 - Crept in at the back post to make it 2-0 and did his part defensively.
Derrick Williams (CB) - 7 - Solid with and without the ball.
Raheem Edwards (LB) - 7 - Didn't quite find his mark with every ball, but always looked to do positive things and caused problems for LAFC.
Rayan Raveloson (CM) - 5 - Caught in possession in the first half but Vela couldn't punish. Sloppy by his standards.
Kelvin Leerdam (CM) - 7 - Played a large chunk of the game in an unfamiliar midfield role but was tidy on the ball and solid without it.
Victor Vazquez (CAM) - 6 - Fit into the system well but didn't come up with many defining individual moments.
Efrain Alvarez (RW) - 5 - A quiet afternoon by Alvarez's standards. Rather frustrating at times.
Chicharito (ST) - 8 - Came up with the opening goal just as we expected the Galaxy talisman to do. Held the ball up well and drew a lot of fouls to gain territory for his team.
Samuel Grandsir (LW) - 9 - A big call to start ahead of Douglas Costa, but Grandsir rewarded Greg Vanney with two fantastic assists in the first half.
Sacha Kljestan (for Araujo, 59 minutes) - 5 - A little sloppy when he came on but did enough to slow things down and keep LAFC out.
Douglas Costa (for Grandsir, 59 minutes) - 6 - Continued to take the fight to LAFC with some direct dribbling.
Kevin Cabral (for Vazquez 67 minutes) - 6 - Had a few dangerous moments and made an impact from the bench.
Nick DePuy (for Williams, 77 minutes) - 5 - Made up for a few nervous moments with a huge block to deny Vela late on.
Dejan Joveljic (for Chicharito 77 minutes) - 4 - Barely got involved.
LAFC player ratings
5. Goalkeeper & defenders
Maxime Crepeau (GK) - 5 - Helpless for the two goals. Cleaned up some long balls behind the LAFC defense.
Ryan Hollingshead (RB) - 4 - Ineffective at both ends of the pitch, leaving too much space defensively and missing his mark with the ball.
Jesus Murillo (CB) - 3 - Hesitated in clearing the ball on the second Galaxy goal, which effectively killed the game.
Mamadou Fall (CB) - 4 - Made a couple of impressive blocks but lost track of Chicharito for the opening goal. Cruelly called offside as LAFC's late equalizer was ruled out.
Diego Palacios (LB) - 6 - Got through his fair share of defensive work and played a smart long throw in the build-up to Arango's goal.
Kellyn Acosta (CM) - 5 - Put in some dangerous deliveries from set pieces but less effective from open play.
Ilie Sanchez (CM) - 7 - So clean and tidy on the ball. Always looked to play the ball forward and unflinching under pressure. The conductor of the LAFC midfield.
Jose Cifuentes (CM) - 5 - Had a couple of dangerous moments but far too quiet overall.
Brian Rodriguez (RW) - 6 - Taken out after just 12 minutes with what looks like a bad hamstring injury. Such a shame given how he can light up fixtures like this.
Carlos Vela (ST) - 6 - Forced the rebound for Arango's goal and had aheader of his own harshly ruled out for offside. By far LAFC's biggest threat.
Kwadwo Opoku (LW) - 6 - Created some dangerous openings and always positive with the ball at his feet, even if he failed with the final ball at times.
Ismael Tajouri-Shradi (for Rodriguez, 12 minutes) - 6 - Looked dangerous on both wings with his dribbling and crossing, despite not quite coming up with a defining moment.
Cristian Arango (for Opoku, 66 minutes) - 7 - Alert to fire in the rebound that put LAFC back in the game. Hopefully a confidence booster for the Colombian.
Latif Blessing (for Cifuentes, 67 minutes) - 6 - Tried to increase the tempo and was harshly denied an equalizer right at the end.