A district court in the Latvian capital Riga found the man guilty of human trafficking and pimping.
The court said that the 46-year-old Finn had taken part in an organised criminal gang that sent dozens of Latvian, Estonian and Russian women from Latvia to Finland to sell sexual services.
What was viewed as particularly serious was that one of the women forced to sell herself by the man was only 17 years old.
The prostitutes serviced clients in rented apartments in different parts of Finland from February 2003 to January 2004.
At the same trial, a Latvian woman was handed a three-year prison sentence. Another Estonian woman was given a suspended sentence of three years imprisonment.
The prostitution ring was uncovered thanks to cooperation between Finnish, Estonian and Latvian police.