The Metropolitan Police was alerted to reports of violence in Woodstock Road at 3.05pm on September 5.
Officers joined London Ambulance Service colleagues at the scene near Mount Pleasant, where a man had been located with serious injuries.
The 45-year-old man has been taken to hospital and is said to have suffered life-threatening and life-changing injuries, the nature of which have not been confirmed.
There have been no arrests and enquiries are ongoing.
A Met spokesperson said: “Police were called at 15:05hrs on Friday, 5 September to reports of violence in Wembley.
“Officers were joined by London Ambulance Service at Woodstock Road, near Mount Pleasant, where a man was found with serious injuries.
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“The 45-year-old man was taken to hospital where his injuries have been said to be life-threatening and life-changing.”
Witnesses or anyone with information are asked to call 101 with the reference 4835/5Sep.
You can also call Crimestoppers anonymously on 0800 555 111 or visit crimestoppers-uk.org.
