The vehicle of the accredited US diplomat hit the pedestrian near Melody Market in Islamabad at 8:30 am, said a statement from the US Embassy.
The pedestrian died as a result of his injuries.
"We extend our heartfelt condolences to the family affected by this tragedy. We have and will continue to cooperate fully with the appropriate Pakistani authorities on the investigation," the statement said.
The embassy said it would work through its local insurance company to "address financial questions or concerns of those affected".