The terminal was temporarily evacuated and the baggage claim and screening areas experienced minor flooding, said airport spokesman Marshall Lowe.
Lowe didn't know how long the sprinklers were on, how many people got wet or have any damage estimates to the airport. Lowe said several flights had been delayed, but was unable to say how many or for how long.
The terminal was evacuated at about 11:25 a.m. PT, and about 30 minutes later passengers were being admitted back into the structure, officials said.
Long lines extended in front of the terminal with passengers who had to go through security checkpoints to be readmitted. Normally busy Sunday morning traffic was especially congested, and police worked to direct cars around the terminal.
Dimity Carlson, 56, who had been visiting Los Angeles with her son, described a chaotic scene where people were rushing toward the doors and knocking over the check-in lines.
"We were inside and there was a rush of people, and they were yelling for us to go outside," said Carlson, from Tampa, Fla.
Carlson and her son missed their flight during the evacuation, and were being rerouted through Las Vegas.
At the Southwest Airlines check-in counter, computers were covered in plastic. The baggage claim area on the lower level was cordoned off, and sawdust and puddles of water lined the floor.
Garbage cans and buckets were spread out in a large section of the baggage claim area, gathering water drops that continued to fall from ceiling tiles.
Kevin Krueger, 32, had been visiting Southern California from Boston to watch a baseball game between the Red Sox and the San Diego Padres.
Having missed his flight, Krueger said he would have to stay in Los Angeles until Monday.
"What a mess," he said, while taking pictures of the damage with his cell phone camera. "The only good thing is I can catch the last game of the series on TV."