The incident happened along Whittlesey Road in Stanground at just before 8am.
Police have confirmed that an “elderly” man has been taken to hospital with serious injuries and that the road has been closed.
They have asked that anyone who may have dashcam incident of the incident to get in touch.
A spokesperson for Cambridgeshire Police said: “We were called at 7.49am this morning (Friday) with reports of a collision in Whittlesey Road, Stanground, involving a pedestrian and a car.
“The pedestrian, an elderly man, has suffered serious injuries and has been taken to Addenbrooke’s Hospital in Cambridge.
“The road has been closed.
“Anyone with dash-cam footage is asked to pass it on to police online at www.cambs.police.uk/report and quote incident 80 of 24 December.”