Cordons have been set up by the Metropolitan Police following the attack on the Caledonian Road in Islington.
It happened at around 10.20am on Saturday.
A man has been arrested on suspicion of attempted murder following the incident.
The Met said the woman's injuries are not life-threatening.
Buses and cars have been diverted away from the scene.
A&E doctor Matthew Swann tweeted: "Major police incident on Caledonian Road N1. Potential stabbing street.
"Two ambulance and police in attendance. Road closure in area. Incident control established.