Police were called to Deacon Road on Monday (August 4) at 2.04pm to reports of a crash involving a pedestrian and a van.
At the scene the boy was found injured and taken to hospital.
His injuries have since been confirmed to be non-life threatening or changing.
The driver of the van stopped at the scene and is supporting police with the investigation.
There have been no arrests at this stage and enquiries are ongoing.
A Metropolitan Police spokesperson said: “On Monday, 4 August at 14:02hrs police were called to Deacon Road, NW2 following reports of a road traffic collision, involving a pedestrian and a van.
”Met officers attended the scene alongside paramedics who treated a 4-year-old boy on scene before taking him to hospital.
”The boys injuries were confirmed to be non-life threating or changing.
“The driver at the van stopped at the scene and is supporting police with their investigation.
”At this stage, there have been no arrests and enquiries are on-going.”
A London Ambulance Service spokesperson said: “We were called at 1.45pm on Monday 4 August to reports of road traffic collision on Deacon Road, Willesden.
“We sent an ambulance crew and an advanced paramedic to the scene.
“We treated a child at the scene and took them to a major trauma centre as a priority.”
Anyone with information is asked to call police on 101 quoting reference CAD4014/4AUG or call Crimestoppers anonymously on 0800 555 111.
