"Accused by Italian authorities of belonging to a criminal organisation, 15 presumed members of the mafia organisation 'Ndrangheta have been arrested, upon orders from the Swiss justice ministry," the ministry said in a statement.
The 15 were all Italian citizens whose extradition has been requested by Rome, the statement said.
Twelve of them were detained in the northern canton of Thurgau, one in the neighbouring canton of Zurich and two in the southern Valais canton, it said.
Italian police believe the group - which they describe as the most active, richest and most powerful crime syndicate in Europe - uses legitimate activities in northern Italy to recycle the huge amounts of cash generated by their drugs business.
Over 140 people were ordered to stand trial at the end of last year for helping the group infiltrate the affluent north, including gangster bosses and businessmen.
Among those detained in Switzerland, two have already been sentenced to six to nine years in prison by the Reggio Calabria court in southern Italy, Tuesday's statement said.
According to the extradition requests, those arrested are suspected of being part of a branch of the powerful 'Ndrangheta organisation based in the northern Swiss town of Frauenfeld.
"Belonging to this criminal organisation means among other things participating in meetings and rituals, submission to hierarchical structures and absolute obedience," the statement said.
Swiss authorities said another two people had also been called in for questioning in connection with the case, but they had not been detained and since they are naturalised Swiss citizens they cannot be extradited.