Mary Donald, 89, of Ellon, was crossing a bridge on the A920 South Road on Saturday when she was hit by a blue Peugeot 208.
She was taken to Aberdeen Royal Infirmary but Police Scotland said she had now died.
Sgt Rob Warnock said: "First and foremost our thoughts go out to the family and friends of Mary."
He said she was well known in the Ellon area.
Officers are continuing to appeal for witnesses.
An elderly woman who was knocked down by a car in Aberdeenshire at the weekend has died in hospital.