Kameron Parchment, 14, was last seen by a friend on the 134 bus at around 5pm on Tuesday heading towards North Finchley.
He was described as wearing black trousers, a white Nike top and black jumper.
Kameron has some knowledge of the Hornsey and Wood Green areas, and may have been in the Friern Barnet and Finchley areas, police said.
Despite appeals on social media, Kameron has not been heard from or seen since January 26.
Kameron’s mum said: “I am absolutely worried sick about Kameron. It is really out of character for him. All I want is for him to contact me, just so I know he is alright.
“Kameron, if you a reading this, please, please get in touch. We all love you very much, we just want to know you’re safe.”
Detective Inspector Jon Moseling of the North West Command Unit which covers Barnet said: “Kameron has been missing for a significant period of time and the longer this goes on, the more concerning it is. I would appeal to anyone who has information about Kameron’s whereabouts to get in touch immediately.
“At the heart of this is a young boy whose family are in shock about him going missing – if you can help us find their son and brother, please don’t hesitate to get in touch.”
If you have seen Kameron or have any information about his whereabouts then call 101 and quote CAD 5391/26JAN. In an emergency or for an immediate sighting of Kameron, dial 999.