The 3.48kg baby, named Lorenzo, was born last month outside the organisation's office here.
The parents of the newborn were driving to hospital when they realised medical assistance would be immediately required.
They pulled over outside the world's largest physics laboratory whose own medical unit and fire service supervised the delivery of the baby.
"Our medical service and ambulance personnel proved to be entirely up to the task," CERN said in its web bulletin.
"In all my 20 years at CERN, I've seen many things, but this is a first," said Veronique Fassnacht, Head of the CERN Medical Service.
"In fact the last time something similar happened at CERN was 40 years ago," said Fassnacht.
"Everything happened very fast but went incredibly smoothly," said Mario di Castro, father of the newborn.
"The CERN Fire Brigade arrived just after the birth and clamped the umbilical cord. Together with the Medical Service they were all very helpful and professional, Castro said.
When the family eventually arrived at the hospital they were told that everything had been dealt with so well that no special additional care was needed, the bulletin said.
Lorenzo, born at CERN's Entrance B on August 26 and his mother are already back home.
