Fuerza Pública officers and health ministry workers cracked down on another chicken-fighting establishment. This one was in Peñas Blancas de Pérez Zeledón.
The ancient blood sport is a firm part of Costa Rican culture. It involves betting, drinking and watching one rooster kill another.
Police said they were tipped by a 911 call, but the location of these sites, called a gallera in Spanish, are well known.
The Servicio Nacional de Salud Animal also was involved in the raid.
Typically the most serious violation was not fighting chickens but the unlicensed sale of alcohol and food. The Municipalidad de Pérez Zeledón is expected to follow up on this case.
Police and animal health workers confiscated 20 live and one dead bird as well as alcohol, they said.
The operation had its own electrical generating setup, and the interior of the structure was air conditioned, said police.
Despite being in an isolated area, there were many persons there and their vehicles.
Although such activities are illegal, expats in the southern zone say those who raise the fighting birds are well-known and that large amounts of money are involved in the wagering.