Iran's only Asiatic cheetah cub died on Tuesday despite days of treatment for kidney failure, Tasnim News Agency reported.
Pirouz, aged 10 months, had been the only survivor of a litter of three endangered Asiatic cheetahs.
“I apologise on behalf of the team since we failed to save his life,” Omid Moradi, the head of Tehran's central vet hospital, told the agency.
Pirouz and the other cats in his litter were the first Asiatic cheetahs born in captivity in Iran, AFP reported.
They were born in the Touran wildlife refuge in Semnan province under close monitoring by Iran's environmental agency.
Iran has long tried to save Asiatic cheetah, one of the world’s critically endangered species. The UN is helping the government step up efforts to rescue the species.
The Asiatic cheetah, an equally fast cousin of the south-east African cheetah, once ranged from the Red Sea to India.
Its numbers have dwindled over the past century to an estimated 50 to 70 animals remaining in Iran.
That number has fallen from as many as 400 in the 1990s. Its numbers plummeted due to poaching, the hunting of its main prey, gazelles, and encroachment on its habitat.
Cheetahs have also been hit by cars and killed in fights with sheep dogs. Shepherds have permits to graze their flocks in areas inhabited by the cheetahs.