Investigators say the 17-year-old worked at the El Coyote Loco Restaurant in Seaford.
They say he set his phone to record and hid it in the bathroom while pointing at the toilet.
Police say an 8-year-old girl found the phone.
They believe it also recorded other women who also used the restroom.
The teen was arrested Saturday night and arraigned Sunday.
He has been charged with three counts of second-degree unlawful surveillance.
Detectives are searching for the other recorded victims.
Anyone who believes they may have been a victim is asked to contact Seventh Squad detectives at (516) 573-6753.
----------
* More Long Island news
* Send us a news tip
* Download the abc7NY app for breaking news alerts
* Follow us on YouTube