The newly arrived baby panda in Washington is male, zoo authorities said Friday, a week after the tiny creature was born along with a twin brother who later died.
The panda born Saturday is doing well, squealing to attract the attention of mother Mei Xiang who is caring for the baby.
DNA testing identified the dad as Tian Tian, a resident panda at the National Zoo, officials said.
"Our ability to assess the cub's lineage will help our colleagues ensure that he finds a suitable mate," Rob Fleischer, head of an evolutionary center at the zoo said.
The paternity test was needed because Mei Xiang had been inseminated twice.
Births in captivity are rare for the black and white giant panda and fewer than 2,000 of the animals exist in the wild.
Giving birth to twins is common, biologists say, but often only one survives because it is difficult for a mother to provide for two newborns at the same time.
The smaller baby panda died of pneumonia on Wednesday despite the zoo's efforts to keep it alive after Mei Xiang chose to care for his larger, healthier sibling.
Newborn pandas, fuzzy and rare, typically cause a public sensation when they come into the world.
After big sister Bao Bao was born in 2013, panda crazed spectators flocked to the zoo and the panda webcam.
More than a million people visited the zoo's panda webcam following the recent birth of twins.
But zoo officials said the panda enclosure will remain closed to the public to allow quiet for mother and cub and visitors will be unable to see the new panda in person before January.
Explore further: Smaller of two newborn pandas at US zoo dies