The suspect grabbed the boy and produced a knife, before escaping on foot with the victim's mobile phone.
Police have released an e-fit image of a suspect - after a 13 year old boy had his mobile phone stolen at knife point.
The attack happened at 5.15pm on Friday January 26, on Reevy Avenue.
The suspect grabbed the victim, produced a knife and demanded his mobile phone - before running off towards Wibsey Park with the mobile.
The victim was unhurt.
The suspect is described as being around 5ft 6ins tall and of slim build.
He was wearing a black hooded top, a brown bomber jacket, black jeans and glasses.
Anyone who recognises him, or may be able to assist in the investigation, is being asked to contact Bradford District CID on 101, quoting crime reference 13180043316.