A list is presented of 242 species of fishes taken in the Golfo de Nicoya, Golfo Dulce and on the Pacific continental shelf of Costa Rica. The specimens were collected using dredges and bottom trawls during December 1993 and February 1994. The Golfo Dulce revealed the lowest diversity with only 75 species represented; 118 species were collected in the Golfo de Nicoya and 129 species in offshore waters. It is presumed that low fish diversity in Golfo Dulce is due to the deep, unproductive waters in that embayment. The checklist includes presence-absence data for each locality.