Police said the teen, 16-year-old Brianna Lane, has been assessed as having the mental capacity of an 8 year old.
Brianna went missing from her home at 261 Whittier Drive in Mastic Beach.
She is described as a white female with a light complexion, approximately 5 feet tall, 165 pounds, with brown eyes and black hair. She was last seen wearing black boots, camo pants, and a black shirt.
Anyone with information on her whereabouts is asked to contact Seventh Squad detectives at 631-852-8752 or call 911.
Silver Alert is a program implemented in Suffolk County that allows local law enforcement to share information with media outlets about individuals with special needs who have been reported missing.