The babies were born by caesarean on Thursday at the Suining City Central Hospital in Sichuan. The twins weighed 9 pounds (4 kilograms) and measured 20 inches (51 centimetres), according to local press reports.
The parents, who are migrant farmers living outside of the southwestern city, did not learn of the abnormality until two days before the mother was due to give birth.
Two ultra sound scans in September and February failed to reveal the two heads because the technicians were viewing the single embryo in profile.
Doctors consider separating the babies, who have separate spines and esophaguses but share major organs, almost impossible.
“It is hard to say how they will survive in the future but we will try the best to keep them alive at the moment,” said Pu Youhua, a doctor with Suining Hospital.
The pair have now been moved to a hospital in nearby Chongqing for further examination.