The last confirmed sighting of 16-year-old Musa Hussain was in Peterborough on January 14.
Musa is from Milton Keynes but as well as Peterborough, has links to Coventry, Rugby and Nuneaton.
Musa is 6ft 1ins tall and slim. When he was last seen, he was wearing a black Nike tracksuit and was carrying a Gucci bag.
Investigating officer, Detective Sergeant Adam Billingham, of Milton Keynes CID, said: “We are becoming increasingly concerned for the wellbeing of 16-year-old Musa Hussain.
“If anyone has any information as to Musa’s whereabouts, I would urge them to contact Thames Valley Police as soon as possible.
“If you see Musa, please call 999. In a non-emergency, you can leave information on our website or call 101, quoting investigation reference 43220062571.”