Prince Watson, who lives in Ealing, was last seen at around 4pm on March 15 in Friern Barnet.
Police have said that the 15-year-old might have since been seen by friends in Hanwell. The teenager also has links to Colindale, Southall and Romford.
Prince is described as being 5’5” tall and of slim build. When he was last seen he had a short back and sides haircut and was wearing a black jacket with grey tracksuit bottoms.
His grandmother has said that his family “love and miss Prince dearly” and that they are “so worried about him”.
She added: “Please take a close look at the photo we are making public today, and don’t think twice about getting in touch if you have any information.”
PC Ben Norris, from the Met’s west area missing persons unit, added: “We are growing increasingly concerned about Prince’s wellbeing.
“Although we have been carrying out a number of enquiries in an effort to find him, we now need the public’s support in bringing him home.”
Anyone who sees Prince has been asked to call 999, quoting reference 2409/07JUNE.
Anyone who believes they have previously seen him or has any other information has been asked to call 101 providing the same reference.
Alternatively, information can be reported anonymously to the independent charity Crimestoppers on 0800 555 111.
