The dawn raid in Palermo netted 80-year-old jeweller Settimo Mineo. He was reportedly elected Cosa Nostra godfather at a Mafia meeting in May.
Italian media describe him as the successor to Toto Riina, who died in jail a year ago.
The Mafia suspects are accused of extortion, firearms offences, arson and other crimes.
The Sicilian Mafia - the Cosa Nostra - managed to rebuild its leadership, known as the Cupola, after it had not met for years, reports say.
Italy's Interior Minister Matteo Salvini tweeted that it was "an extraordinary intervention" by the Carabinieri (the country's police), "who have dismantled the new 'cupola' of Cosa Nostra".
In recent years police have hit the Cosa Nostra network hard, but it has been trying to rebuild its leadership, Italian media report.
'I fell from the clouds'
Cosa Nostra was long handicapped by the fact that Toto Riina was in jail, but when he died the Mafia moved to rebuild the cupola without taking orders from a "godfather".
On Instagram, Deputy Prime Minister Luigi Di Maio said "there is no more room for this type of scum in Italy".
Riina was notorious for his brutality. In 1992 two leading prosecutors, Giovanni Falcone and Paolo Borsellino, were blown up in Mafia hits. Six months later Riina was arrested.
Italian daily newspaper La Repubblica says Settimo Mineo was arrested on Falcone's orders in 1984, and told his interrogators: "I don't know who you're talking about, I fell from the clouds."
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