More than 3 million people were registered to vote at 2,115 polling stations, the Supreme Electoral Tribunal said.
Four of the presidential front-runners attended mass Sunday at the Metropolitan Cathedral, calling for dialogue and understanding, La Nacion reported.
"We are interested in Costa Rica succeeding, it is a chance to promote dialogue," said Citizen Action Party candidate Luis Guillermo Solis said.
Social Christian Unity Party candidate Rodolfo Piza called for a message of respect and solidarity.
"Understand each other and respect one another to together build a better country," he said.