The 19-year-old victim was walking along Ellen Road at the junction with Brent Park when he was approached by a man.
The robber demanded the victim’s phone, which he refused to hand over.
He was then punched in the chest and stomach before having his phone taken.
The offender walked off up Ellen Road.
The victim did not need hospital treatment.
The robbery happened at about 3.30pm on Monday.
The robber is white, about 18 years old, approximately 5ft 8ins tall, of medium build with brown eyes and fine facial hair.
He was wearing a grey hooded top with stripes down the arms and an Adidas logo on the chest, light grey jogging bottoms and white trainers.
Anyone with information should contact investigator Tina Scott on 101 or Crimestoppers anonymously on 0800 555 111.