Police restrained the man and he was taken to a major trauma unit where his injuries were not deemed to be life-threatening.
Brent MPS tweeted: “A crime scene is in place in St Marys Road, Brent, after a man was found with stab injuries.
“The man was restrained by officers, who believed he had a serious injury, after he refused treatment.
“He was taken to hospital.
“His injuries were assessed as non life-threatening.”
Photos of the scene showed officers guarding a police cordon.
The tape extended around cars parked near a coronavirus testing centre.
Police remained at the scene in St Mary’s Road, opposite St Margaret and St George’s Church, and just off the busy Craven Park Road on Monday afternoon.
In a statement, the Met said the stabbing victim is aged in his 20s.
The statement read: “Police were called by London Ambulance Service (LAS) to St Marys Road, NW10, at 1.35pm on Monday August 17 to a report of a man with stab injuries.
“Officers attended. A man in his 20s was found injured.
“Due to the fact officers believed he had a serious injury and he was trying to get away from emergency services, the man was restrained and then put in an ambulance and taken to hospital.
“His injuries have been assessed as non life-threatening.
“Enquiries into the circumstances continue.”
A spokesperson for the London Ambulance Service said: “We were called at 1:30pm this afternoon (August 17) to St Mary’s Road, NW10, to reports of a stabbing.
“We dispatched an ambulance crew and a medic in a response car to the scene.
“We treated a man and took him to a major trauma centre.”
The knife attack comes just over a week after a teenager was knifed to death in front of shocked shoppers off Oxford Street.
Seventeen-year-old Jeremy Menesses was knifed on Market Place on August 8.
The Met said the attack happened “following a fight between a number of males” which had been “witnessed by a large number of horrified onlookers”.