Judicial police raided two apartments in the southern part of the capital and found drugs and an assortment of firearms.
Agents said that one of the two apartments was used as a storage area for the weapons and some of the drugs. They said they confiscated six kilos of cocaine.
The apartments were in Barrio Cañada del Sur. The 43-year-old woman had three pistols, two AK-47s, an Uzi submachine gun, and what was described as a Russian machine gun. Automatic weapons are illegal in Costa Rica.
The Judicial Investigating Organization said the weapons would be submitted to tests to see if they had been used in any crimes that are under investigation.