Detectives say two 16-year-olds were approached last month by a group of seven other teens at the restaurant on W. Merrick Road in Valley Stream.
Police released surveillance video of the incident as the group began assaulting the victims, causing both of them to suffer contusions and lacerations to their heads.
Watch the full video here:
Raw video: Brawl inside Long Island Burger King
After the assault, the subjects fled the restaurant in an unknown direction.
Both victims, who suffered non-life threatening head injuries, were transported to an area hospital for treatment.
Police are trying to figure out what sparked the attack.
Detectives request anyone with information regarding this assault to call Crime Stoppers at 1-800-244-TIPS.