The firefighter was burned on his hands and arm and was taken to the hospital in fair condition. No other injuries were reported.
The blaze started at about 3 a.m. in the 20800 block of Sherman Way, according to officials from the Los Angeles Fire Department.
It took more than 100 firefighters about one hour to knock down the flames, officials said.
Several lanes of Desoto Avenue and Sherman Way were temporarily shut down while firefighters mopped up the scene.
Fire officials said there are four businesses inside of the strip mall. The interior locations, including a check-cash business, had the most damage.
"The check-cashing place and the cash-for-gold place are more heavily damaged and it's going to take a long time. They're going to have to go through that whole fire rehabilitation process," said Capt. Daniel Curry of the LAFD.
The cause of the blaze was under investigation.