The 46-year-old victim was attacked as he was walking home in the Waterford Street area of west Belfast at around 2.30am.
He was approached by a man who demanded his phone and when he refused, the attacker stabbed him in the chest and made off with the phone.
The injured man was taken to hospital where he is said to be in a serious but stable condition.
A PSNI spokesperson said the victim’s injuries are not believed to be life-threatening.
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