A group of at least eight women gathered around display cases and shoved several sunglasses and other merchandise into their bags at about 2:50 p.m. March 29 in the Westfield Valencia Town Center.
The store clerk quickly realized what was happening and dialed 911, detectives said.
Josh Dubin, a spokesman for the Los Angeles County Sheriff's Department, called the incident a very "brazen" theft that occurred in broad daylight.
The women were between 18 and 25 years old and may have gotten into a dark-colored SUV-type vehicle, Dubin said.
Anyone with information about this crime should call Los Angeles Regional Crime Stoppers at (800) 222-TIPS (8477).