Midland Detectives are calling on the public to help with information about a robbery in Bassendean last month.
About 12.30pm on November 24, a 19-year-old man was walking along Anzac Terrace when two men on a dark-coloured scooter approached him and demanded he hand over his mobile phone.
The passenger got off the scooter and threatened the teenager with violence, prompting him to hand over his phone.
The offender is described as dark skinned with short, black hair with a rat's tail, and about 180cm tall of a slim build.
Anyone with information is asked to call Crime Stoppers on 1800 333 000.