Matteo Messina Denaro, 53, who has been on the run since 1993, used a farm in Mazara del Vallo to communicate with his henchmen via the aged-old method of "pizzini", bits of paper containing messages often written in cipher, police said.
Among those arrested was former boss Vito Gondola, 77, whose job it was to call the clan members to alert them to each new message, which was placed under a rock in a field at the farm and often destroyed on the spot after reading.
"The sheep need shearing... The shears need sharpening" and "the hay is ready", were among other code phrases used to alert the gang to a new message, written on tightly folded bits of paper wrapped in Sellotape and then hidden in the dirt.
The police investigation, which followed the passing of messages between 2011 and 2014, used hidden cameras and microphones around the farm near Trapani in western Sicily to follow the movements of the clan - and discover Denaro's fading glory.
Three of those arrested were over 70 years old.
The only known photos of Denaro date back to the early 1990s. He is believed to be the successor of the godfathers Toto Riina and Bernardo Provenzano, who are both serving life sentences, but less is known about him.
At the height of his power he had a reputation as a flashy, ruthless womaniser who ruled over at least 900 men with an iron fist.
Prime Minister Matteo Renzi thanked the investigators in a message on his Facebook page, saying "onwards all, to finally capture the super-fugitive boss," insisting "Italy is united against organised crime" despite a recent slew of corruption scandals in the country.
"The state wins, the Mafia loses," Interior Minister Angelino Alfano said on Twitter.
