The victim, in his 20s, was rushed to hospital after being knifed on West Green Road, Tottenham, at 1.30pm on Friday.
Police said they are awaiting an assessment of his condition.
An urgent investigation is underway and officers remain at the scene.
So far there have been no arrests.
Witnesses or anyone with information is asked to contact detectives on 101 quoting: CAD 3665/30OCT.