The incident happened in Walm Lane near St Pauls Avenue just after 9pm yesterday (June 25).
Officers and London Ambulance Service crews attended and found four people injured.
Two 21-year-old men and a 20-year-old man were taken to hospital with stab injuries.
Their conditions are unclear at this stage.
A 20-year-old woman who reported breathing difficulties declined medical treatment at the scene.
Another person was taken to a local hospital for treatment.
The road was cordoned off for several hours while forensic officers gathered evidence at the scene.
No arrests have been made as police enquiries continue.
A London Ambulance Service spokesperson said: “We were called at 9.02pm on Wednesday 25 June to reports of a stabbing on Walm Lane, NW2.
“We sent a number of resources to the scene, including ambulance crews, an incident response officer, a clinical team manager and paramedics from our tactical response unit.
“We also dispatched trauma teams in cars from London’s Air Ambulance.
“We treated four people in total. We took two patients to a major trauma centre and another patient to a local hospital.
“The fourth person declined further treatment.”
