The calf, whose gender is not yet known, was born Saturday to mother Tessa and father Kimba, both 4 years old, The Cincinnati Enquirer reported.
The parents and the new calf are the only giraffes at the Cincinnati Zoo.
The calf was on its feet taking its first shaky steps about 20 minutes after the early morning birth and was nursing within an hour, zoo officials said.
"When there's a birth of an animal, it's awe-inspiring because nature is a phenomenal system," zoo Executive Director Thane Maynard said. "That's true when a mouse is born, but when you've got a 6-foot baby that comes out and flops on the ground, it's just the darndest thing. It goes without saying, this is an exciting day."
The baby had not been named and no attempt to ascertain its gender had been made, zoo officials said, to give mother and baby time to bond without being disturbed.