The former France international, who has played club rugby in three different countries, put pen to paper on a two-year contract with Gloucester in 2006 and signed a one-year extension last year.
But having called time on his international career last year, Califano is set to hang up his boots for good at the end of the current campaign.
"Honestly, it's my last year," he told L'Equipe.
"I have had the fortune to play for three great clubs in my career, Toulouse, Auckland and Gloucester.
"I will close the door in the best possible spirit and with nothing but happiness and good memories filling my head."
Califano won 72 caps for France - making him the most-capped French prop of all-time along with Sylvain Marconnet.
One of the giants of the scrum, he played his first and last internationals against the All Blacks over a 13-year period.
The 35-year-old enjoyed a glittering career since starting out at Bourges in 1991 - counting six French titles and one European Cup at Toulouse as well as two Grand Slams among his illustrious haul.
Califano also holds the record of being the first frontrower to score three tries in a match - against Romania in 1996 - and the first French player to feature in the Super 14 championship with Auckland.
The lowest point in his career came in the 1999 World Cup when he was banned for seven weeks for headbutting an opponent in a group match against Fiji.