The accident happened near Sunken City Trail. Fire officials say a group of family members were walking down the trail. The little girl slipped and fell 15 to 20 feet.
Rescuers were able to reach her and she was transported by helicopter to Harbor-UCLA Medical Center. Hospital officials say she suffered head injuries and is in critical condition.
What caused her to fall is unclear.
The Point Fermin cliffs have a history of fatal falls, including the 2007 death of University of Southern California kicker Mario Danelo.
The Associated Press contributed to this report.