The women were freed from brothels in Malaga and Girona where they had been sexual exploited by their compatriots and made to work for up to ten hours a day under the threat of violence.
Some had come to Spain after being falsely promised better lives by the Romanian sex traffickers while others had fallen victim to the so-called 'lover boy' scam, according to a police statement.
This method involves one of the sex traffickers forming an intimate relationship with the woman to earn her trust before later forcing her into prostitution.
One of the women freed, who was only 18 years old, had been reported as missing by her family in Romania.
Police described the 'iron control' exerted by the 'well-organized' sex-trafficking ring and said that the women had been kept completely isolated from the outside world.
They were moved around at the whim of the traffickers between brothels in Lloret de Mar in northern Catalonia and Malaga in southern Andalusia.