The little girl, called Hong Hong, was born with the tail but it had since doubled in size, reports the Anhui Market Daily.
Her father, Hou, of Lixing town in eastern China’s Anhui province, said he had been “shocked” to see the tail at birth.
“I wanted to cut it off when she was born, but doctors suggested we wait some time, as a newborn is too weak to take such a surgery,” he said.
He checked the tail each day, hoping it would get smaller but instead it just “grew bigger and bigger”, he added.
Doctors at the Anhui Provincial Children’s Hospital said they too had been surprised by the case.
“It’s very rare, about one in a million. We have never seen anything like this before,” said Dr Sun Jun.
X-rays had shown that the tail was connected to a fatty tumor within the spinal column.
Dr Sun said the surgery had been successful, but it was still too early to say whether further treatment would be necessary.