Police are appealing for public assistance to help locate missing teen Joshua McCracken.

The 13-year-old was last seen in Waterwheel Grove, Mernda yesterday (Tues.) at 8am.

Family and police hold concerns for Joshua due to his age and as he has medical conditions.

Joshua is known to frequent the Doreen, Mernda, Thomastown, Lalor and Reservoir areas.

He was last seen wearing black tracksuit pants, a black hooded jumper and black runners.

He is described as Caucasian in appearance with a slim build and short, light brown hair.

Police have released an image of Joshua in the hope that someone may recognise him.

Anyone who sees Joshua is urged to contact Mernda Police Station on 9216 1200.