Kyle Collins has been missing from an address in Newcastle since the December 5.
Police say the 15-year-old is believed to have made his way to Preston.
A spokesman for the police said: "We are becoming concerned for the welfare of a 15 year old male, named Kyle Collins who has been missing from an address in Newcastle.
"Kyle is known to have links to Preston and it is thought he has made his way to the area.
"Anybody with information on the location of Kyle should contact police."
The police can be contacted on 101 quoting log number LC-20171205-1451.