At least eight police cars are on the scene, with the restaurant closed to the public.
Metropolitan Police are asking people to avoid the area, including local restaurants, as roads are closed.
An air ambulance was seen hovering overhead.
Are you at the scene? Did you witness the incident? Email [email protected]
A man in his 20s was stabbed in the incident, according to a BBC reporter.
No arrests have yet been made.
Anyone with information is asked to call 101 and quote CAD 7150 / Aug 10.
A local witness claims the injured man was seen running into Colindale McDonald’s after being stabbed in an area across the road.
“I was sitting inside and heard all those police sirens. I saw two cops rushing into the McDonalds with stunned people crowding outside, ”they told the Daily Star.
“It happened in broad daylight. It’s horrible. I was told the person had been stabbed in our property, then crossed the road and stumbled upon McDonald’s.
“The whole area is now registered awaiting forensics. We cannot go in or out.
“Two years ago there was another stab in here and the guy died. People no longer feel safe. ”
“Then the air ambulance got off and the paramedics ran to help.
A Metropolitan Police spokesperson said: Police were called at around 6:40 p.m. on Monday August 10 for reports of a man being stabbed in Colindeep Lane, NW9.
“Officers and the London ambulance service were present and the man, who is believed to be 20, is being treated at the scene.
“Closed roads, including local businesses around the junction with Zenith Close, remain closed.
“Investigations into the circumstances are continuing. “
Colindale was the scene of unrest earlier this week when around 40 people gathered outside the police station.
They were protesting what they saw as the inappropriate treatment of a 14-year-old boy who had been arrested, My London reported.