Police are asking for assistance to locate 15-year-old Aaliyah, who was last seen on Francis Cr, Mount Evelyn on Monday 1 May.
Aaliyah wore black tracksuit pants, a red T-shirt, a grey zip-up jumper, a green puffer jacket and a black Adidas jumper.
Police and family have concerns for her welfare due to her age and medical condition.
Anyone with information on her whereabouts is urged to contact Mooroolbark Police Station on (03) 9725 9999.