Dr. Victor Willoughby, who tested positive for Ebola on Saturday, died on Thursday, Dr. Brima Kargbo, the country's chief medical officer said.
Dr. Victor Willoughby, was a top Doctor in Sierra Leone before contracting the disease on Saturday and who eventually died on Thursday before the experimental drug could be given to him.
So far Eleven doctors have died of Ebola in the west African country.
She added that "Dr. Victor Willoughby was a mentor to us physicians and a big loss to the medical profession," said Kargbo.
"He has always been available to help junior colleagues."
The arrival of ZMAb, developed in Canada, had raised hopes for Willoughby's survival. But he died before a dose could be administered, said Kargbo.
Ebola has taken a particular toll on health workers, killing more than 350, depleting the ranks of doctors and nurses in countries that already had too few to begin with.
The disease is now spreading fastest in Sierra Leone, but the World Health Organization says there are signs the infection rate may be stabilising there.