Gagliano, convicted of three murders as well as a slew of other crimes, was allowed temporary leave to visit his mother in Savona as a reward for good behaviour over the past three years, but he instead hijacked a bakery delivery van at gunpoint and told the driver to head to Genoa, La Stampa reported.
Once in Genoa, he let the delivery man go and made his escape in a green Fiat Panda.
Staff at Genoa's Marassi penitentiary said they had no idea that Gagliano, 55, was a convicted serial killer when they granted him leave.
“We did not know he had this criminal history, for us he was a robber,” prison warden Salvatore Mazzeo told La Stampa.
Justice Minister Annamaria Cancellieri said the incident is “very serious” and requires a “rigorous assessment”.
“It’s useless to deny that this will be a blow to our attempts to make prisons more civil and able to fulfill their rehabilitative function.”
Gagliano, who also escaped from a psychiatric hospital in 1989, killed two prostitutes and a man between 1981 and 1989. He was also convicted of attempted murder as well as robbery and the possession of drugs and weapons.