Police have been called after a foreign national was robbed at knifepoint outside the Tesco express on Kingsbury Road in Kingsbury on Tuesday evening.
The man demanded cash and the man phone whilst holding him at knifepoint outside the supermarket just before 11pm.
The man is described as black.
The victim was unhurt by his ordeal and has been taken by police to give a fuller description and circumstances.
The Met police have been contacted for a statement.