The raids were in the region around Trapani in western Sicily, the police said in a statement, hailing the "tough blow" to Messina Denaro's organisation.
Messina Denaro, who has been on the run for years, is believed to be the successor of the jailed Sicilian mafia godfathers Toto Riina and Bernardo Provenzano.
The people arrested "had put in place a complex system of companies thatgave them a virtual monopoly in the construction sector," the police said.
The criminal organisation won tenders to build wind farms, industrial areas, roads and restaurants.
The police said their investigation showed "the leadership role played by Matteo Messina Denaro".
The suspects are also accused of large-scale extortion.