The incident between a pedestrian and a car happened in Grafton Road just before 8.40am today (January 24).
Officers, London Ambulance crews, paramedics in fast response cars and an incident response officer were dispatched to the scene.
The child was found injured near Grafton Primary school and was treated before being taken to hospital as a priority.
His injuries are not believed to be life-threatening, and no arrests have been made.
A Met Police spokesperson said: “Police were called to a report of a collision involving a boy and a car on Grafton Road, Dagenham at 08:38hrs on Friday, 24 January.
“The boy, aged four, suffered non-life-threatening injuries and was taken to hospital.
“No arrests were made and the road is now open.”
A spokesperson for the London Ambulance Service said: “We were called at 8.37am this morning (Friday 24 January) to reports of road traffic collision in Grafton Road, Dagenham.
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“We sent resources to the scene, including ambulance crews, paramedics in fast response cars and an incident response officer.
“The first of our crews arrived in three minutes.
“Our crews treated a child at the scene, before taking them to hospital as a priority.”
