The coin was likely struck in 56-57 AD, researchers say. The Romans took control of the city in 63 BC after what became known as the Siege of Jerusalem.
"The coin is exceptional because this is the first time that a coin of this kind has turned up in Jerusalem in a scientific dig," said Shimon Gibson, co-director of the excavation.
"Coins of this type are usually only found in private collections, where we don't have clear evidence as to place of origin."
One side of the coin, known in Latin as an aureus, shows a portrait of Nero as Caesar. Many Roman emperors took the title of Caesar or Augustus to mean emperor.
The lettering around the edge says "NERO CAESAR AVG IMP," referring to his name and position. The reverse of the coin shows an oak wreath with the letter "EX S C" and "PONTIF MAX TR P III," which allowed archaeologists to date the coin.
The coin was discovered at the Mount Zion archaeological dig, south of the Old City of Jerusalem, where a University of North Carolina-Charlotte team has been excavating throughout the summer.
"Because it is gold, there is no erosion," said Rafael Lewis, a professor of archaeology at the University of North Carolina-Charlotte. "You can see the name of Nero, the fact that he was an emperor, and everything is there. Every bit of information is clear. Unlike bronze coins or silver coins, this one doesn't erode."
"The gold is also of a very high quality. We are talking about 24 carats," Lewis added. "99% of the coin is gold."
The location of the find suggests that large houses in the area may have belonged to the wealthy priestly caste, Gibson said, and the coin may have come from one of their homes.
There is no evidence that Nero ever visited Jerusalem, Gibson said.
Nero served as Emperor of Rome from 54-68 AD, after rising to power as a teenager. He was known for his lavish spending -- often on himself -- at the expense of the Roman population, and for his cruelty. The Roman historian Tacitus reported that Nero even had his mother and wife put to death.
Nero ruled during Rome's Great Fire in 64 AD, when parts of the city burned for five days. Many Romans held him responsible for the fire, Tacitus wrote, believing he burned down the city so he could rebuild it to his liking.