The incident happened in Stonegrove at around 5.30pm yesterday (January 9).
Officers and the London Ambulance Service attended the scene and treated a man before taking him to hospital.
He remains in hospital in an unknown condition.
The driver of the car stopped at the scene.
Police are appealing for information which may be able to assist in the ongoing investigation.
A Met Police spokesperson said: “Police were called to the Stonegrove, Edgware, HA8 at 17:30hrs on Friday, 9 January following a collision between a car and a pedestrian.
“Officers attended the scene alongside the London Ambulance Service who treated a 91-year-old man before taking him to hospital where he remains.
“We await a full condition update.
“The driver of the car stopped at the scene.
“An investigation has been launched and police are appealing for information.
“Anyone who has any information about the incident, or has any dashcam footage should contact the witness line on 0207 960 8044 quoting 5368/9JAN26.”
