Officers swooped down on a house in Magadino, near Locarno, where six Romanian women were found with eight clients, cantonal police said on Thursday.
Four of the prostitutes were caught “in flagrante delicto” with customers, police said.
The raid took place on Wednesday night as part of Operation Domino, a campaign to root out illegal prostitution in the canton.
The manager of the Magadino house, a 52-year-old Lugano man, was questioned and charged with promoting illegal prostitution before being released, Ticino police said.
The six women were reported to immigration authorities for unlawful prostitution.
Police said only two of them had proper permits.
A woman inspector from the Romanian national police was involved in the operation.
She works with a division of the force dedicated to combatting organized crime and human trafficking.
International policing cooperation of this nature is being coordinated by a working group set up by Simonetta Sommaruga, federal minister of justice and police.
Operation Domino has led to the closure of more than two dozen prostitution rings.
The Ticino prosecutor estimated that 182 people had been arrested between March and July this year alone, including 170 women.
Rival gangs from Eastern Europe have become increasingly involved in illegal prostitution rings in Ticino, according to police reports.