Sheriff's deputies say the victims were barbecuing when two men approached and opened fire, hitting the two men and the toddler.
The two men died at the scene.
The two-and-a-half year old child was taken to Long Beach Memorial Hospital and is expected to survive.
"They found that there were two adult males that had been shot at the rear of the location as well as a two and a half year old infant. Both males were deceased at the scene. The two that were shot were neighbors. They were celebrating a backyard barbeque," according to Lt. Pat Nelson of the Los Angeles County Sheriff's Department.
"She was holding the baby in her arms and in the back of the baby, you could see the bullet hole which was very sad," said neighbor Carlos Pacheco. "She kept on telling the baby, 'Hold on, hold on, you know. Hold on, baby, hold on baby."
The two gunmen ran away.
Police do not have a motive and have not yet released the names of the victims.