The Met Police were called shortly after 4.30pm following reports of a stabbing incident around Dobson Close in Swiss Cottage. Officers and ambulance crews attended the scene and found a 15-year-old boy with a stomach wound.
The force said the teenager was treated at the scene and has been taken to a local hospital.
His condition is not life threatening or life changing, police said.
The Met Police added an investigation remains ongoing.
Officers have urged anyone with information to come forward.
Crews from the London Ambulance Service and the Air Ambulance Service also attended the incident.
In a statement, the Met Police said: “Police were called at 16:31hrs on 23 June to a report of a stabbing around Dobson Close, NW6.
“Officers attended along with colleagues from the London Ambulance Service and the Air Ambulance Service and treated a 15-year-old boy with a stomach wound.
“The exact circumstances are still under investigation.
“The injuries are not life threatening or life changing. He was taken to a local hospital.”
The incident caused some concern amongst Londoners in the area, with many taking to social media this afternoon.
One user shared a picture of at least two police vans and one police car being deployed to the incident.
They tweeted: "Some serious police presence on Swiss Cottage. Heard it was about a stabbing."
Another user wrote: “They tweeted: “Does anyone know what all the sirens and massive helicopter around Swiss Cottage/St John’s Wood is all about?”
The Met has called on anyone with information to contact the force 101 with the reference 5349//23Jun.
Alternatively the charity Crimestoppers can be reached anonymously on 0800 555 111 or online at crimestoppers-uk.org.