Beckham got into the friendly against Chelsea in the 78th minute, jogging onto the field amid huge cheers and a sea of camera flashes from the sold-out crowd of 27,000 at Home Depot Center.
"The atmosphere is incredible," he said after Chelsea's 1-0 victory. "It made me feel a little bit embarrassed at times."
The 32-year-old midfielder spent most of the game on the bench because of a nagging left ankle injury.
"The objective was just for him to be on the pitch and give the people the dessert they were looking for," Chelsea coach Jose Mourinho said.
There were cheers each time Beckham touched the ball, the highlight being a corner kick he took in stoppage time.
Landon Donovan, who usually handles such kicks, gave way to Beckham, who said, "I was happy because I didn't have many touches on the ball."
Beckham's only physical contact was when Chelsea's Steve Sidwell attempted to tackle him.
"I saw him coming and I jumped just in time so my foot wasn't planted when he hit me," Beckham said.
After taking about 10 minutes to get loose on the sideline, he entered as a substitute for Alan Gordon, who slapped hands with the English superstar before Beckham took the field for the first time.
"I'm not fit. I haven't trained since I got here," he said. "But it's nice to be out there."
Chelsea captain John Terry scored in the 49th minute on a shot that ricocheted off the right post and left post before caroming into the net.
"Speaking as an Englishman, it was great to see him come on," Terry said. "Everyone can see what he can do. He's going to take it (soccer) to another level. He's a world-class player and I'm sure a lot of players are going to be attracted to the MLS now."
Beckham got off the bench in the 66th minute to warm up, exciting fans who had waited most of the game to see him. He jogged up and down the sidelines and a roar went up when Beckham tapped an out-of-bounds ball back to the referee, his first kick of the night.
He briefly ran off the field with the Galaxy's trainer before returning and peeling off his warmup shirt to reveal his favored long-sleeved jersey on a warm night when the other players wore short sleeves.
He said he went inside to use the bathroom and get his ankle re-taped.
"I didn't want to do it in front of the whole world," he said.
Beckham's debut was crazy from the start. When he took his seat on the end of a metal bench, he was quickly surrounded by about 100 photographers pushing and shoving to get a shot.
He calmly took in the scene as the scrum furiously snapped away within inches of him before being shoved back by about 10 security guards. He chatted with teammate Peter Vagenas while the Galaxy's starting lineup on the field was all but ignored.
Beckham's wife Victoria, wearing her trademark huge black sunglasses, along with actress Katie Holmes and her infant daughter Suri, watched from a private box above the field. Actress Jennifer Love Hewitt was like a lot of spectators, attending her first soccer game.
Actress Eva Longoria, minus new hubby Tony Parker, comedian Drew Carey, NBA star Kevin Garnett, movie producer Brian Grazer, California Governor Arnold Schwarzenegger and English actors John Hurt and Ray Winstone also made what were likely their first trips to Carson, a downright gritty suburb compared to the stars' usual haunt of Beverly Hills.
Beckham displayed his famous fashion sense at a post-match news conference, appearing dapper in a blue-and-white shirt, buttoned navy cardigan and navy slacks.
"The attention has been immense," he said. "I have to say thank you to everybody."
As he exited the interview tent, fans waiting outside began running after him and screaming.