The victims, a boy and girl, were rushed to the hospital to undergo emergency surgery. Their conditions were not known.
Police said the mall was contained and searched, but the suspect got away.
"We were searching cars that were leaving, searching people that were coming out of the theaters," said Sgt. Shawn Freeman of the Redondo Beach Police Department. "We had a very vague suspect description. We knew we had two people that had been stabbed so we were hoping to find evidence or maybe some witnesses or somebody that saw something."
The suspect was described only as a black male.
Police said they are asking for witnesses to come forward.