Fifty-one genera of Encyrtidae (Insecta;Hymenoptera) known to occur in Costa Rica, belonging to ten tribes of the subfamily Encyrtinae, are characterised by means of generic diagnoses. Their biology and use in biocontrol are summarized for every genus and identification keys to the 316 Costa Rican species are provided. All species are illustrated and defined by means of brief diagnoses or full morphological descriptions, and information is provided on their known distributions, host ranges, and use in biocontrol.