Police are concerned for the welfare of Gbombo Neba, 16, who has been missing from his Henfield carehome since Thursday August 9.
Gbombo is originally from the Waltham Forest area of London but recently moved to West Sussex.
He is described as Afro-Caribbean, 6’, of stocky build with short dark brown hair and speaks with a London accent.
He was last seen on August 9 near Lancing Railway Station and was wearing blue jeans, black trainers and a brown jumper.
PC Ollie Pullen, of the Horsham Neighbourhood Response Team, said: “Due to Gbombo’s age and now the length of time he has been missing we are becoming increasingly concerned for his welfare.
“Since Gbombo was reported missing Sussex Police, with the help of the Metropolitan police, have pursued a number of enquiries in order to try and locate him.
“We are now appealing to the public for any information relating to his whereabouts as we believe he may still be in the Worthing area. Please contact Sussex Police on 101 quoting serial 1723 09/08.”