There was no immediate word on the cause.
The Washington Post said zoo staff heard "distressed vocalizations" from the female giant panda Sunday morning and realized something was wrong. The staff then noticed the cub was not emitting healthy squeals.
Zoo officials retrieved the cub from the den using a pair of cushioned grabbers, and veterinarians tried performing cardiopulmonary resuscitation, or CPR, but the little animal could not be revived, the Post said.
It was the first giant panda cub born at the zoo since 2005, the newspaper said.
A newborn red panda cub died at the zoo in 2010, the first born at the zoo in 15 years. A definite cause of death was never determined, but half of all red pandas born in captivity die.