Adalet Kaya was last seen in Moonee Ponds on 18 August about 2:30pm.
She was wearing a dark blue Kathmandu puffer spray jacket, a white t-shirt and black jeans.
Adalet is about 150cm tall, with a thin build, black hair, brown eyes and olive complexion.
Police hold concerns for her welfare due to her age.
Adalet is known to frequent the Broadmeadows and Moonee Ponds areas.
Anyone who sees Adalet should call Moonee Ponds Police Station on (03) 9373 5200.