The incident happened between High Road and Broad Lane just before 6.50pm on March 31.
Officers and London Ambulance Service crews attended and found a 12-year-old injured.
He was taken to hospital for treatment where his condition is currently being assessed.
No arrests have been made as police enquiries continue.
A spokesperson for Metropolitan Police said: “Officers responded to reports of a collision involving a car and a cyclist on the junction between High Road and Broad Lane, Tottenham at 6.53pm on Monday, March 31.
“The cyclist, a 12-year-old boy, was treated at the scene for injuries and later taken to hospital by the London Ambulance Service.
He remains there for treatment and we await an update on his injuries and condition.
“An investigation is underway and no arrests have been made at this stage.”
A London Ambulance Service spokesperson said: “We were called at 6.49pm to reports of a road traffic collision in High Road, Tottenham.
“We sent resources to the scene, including ambulance crews, a paramedic in a fast response car and London’s Air Ambulance.
“The first of our crews arrived in less than a minute. Our crews treated a child at the scene, before taking them to a London major trauma centre.”
