The 32-year-old, hampered by an injured left ankle for the last two months, left the pitch in the 63rd minute after inspiring a 2-0 win over D.C. United in a SuperLiga semi-final.
Wearing his number 23 shirt, Beckham opened the scoring with a superb free kick in the 27th minute to spark wild cheering from a crowd of 17,223 at the Home Depot Center.
The former England captain curved one of his trademark strikes into the top left corner of the net from 25 metres, leaving goalkeeper Troy Perkins stranded.
Despite having played only 37 minutes in two fleeting appearances for the Galaxy since joining them last month, Beckham came back out for the second half and made an early impact.
In the 47th minute, he threaded a precise through ball for US international Landon Donovan who shrugged off two defenders before driving the ball low past Perkins into the right side of the net.
Beckham, who was yellow-carded in the in the 18th minute for a mistimed tackle on D.C. captain and forward Jaime Moreno, produced one more moment of magic before he left the pitch.
In the 58th minute, he took his second free kick of the match but his bending effort was brilliantly saved by Perkins diving to his right.
CHEERED LOUDLY
Beckham
Signed from Real Madrid on a $32.5 million five-year deal, Beckham had spent most of his first three weeks in Los Angeles receiving ice treatment and massage in the treatment room or working in the gym.
He twisted his ankle playing for his country against Estonia in a Euro 2008 qualifying match in June and aggravated it in his final appearance for Real 11 days later when his former team clinched the Spanish league title.
If Galaxy fans had become frustrated by Beckham's relative inactivity in his first month with the Major League Soccer club, they were treated royally on Wednesday.
The former Manchester United and Real Madrid player prompted a huge roar from the crowd when he led the team on to the pitch for his long-awaited first start for the club.
Beckham was partnered in midfield by Donovan, the Galaxy's usual captain, and made his first impression on the match with his opening corner kick in the 13th minute.
From the right, he delivered a Beckham special but his team mates failed to capitalise as the ball swung across the front of the United goal.
Galaxy fans enjoyed a brilliant move in the 20th minute when Donovan shimmied past two D.C. defenders and slid a pinpoint pass for Beckham to chase on the right wing.
Beckham's cross forced another corner kick for him to take but this time the United defence held firm.
Photograph: Getty Images | Text: Reuters