This contribution focuses on the family Encyrtidae from Oslo Municipality, one of the richer areas in Norway as biodiversity concerns. The following four species are reported for the first time from Norway: Metaphycus punctipes (Dalman, 1820), Protyndarichoides aligarhensis (Fatma & Shafee, 1985), Psyllaephagus belanensis (Hoffer, 1963) and Trechnites trjapitzini Sugonjaev, 1968, and one additional species, Blastothrix osloensis sp. n., is described and illustrated. This brings the total number of Norwegian encyrtids up to 141, and 30 of these are recorded from Oslo Municipality. Comments on biology and distribution of the species are given. The aim of this study is to highlight the distribution of Encyrtidae in Norway, and to provide a complete list of the Norwegian species. Posted here with permission from the journal. Norwegian Journal of Entomology: http://www.entomologi.no/journals/nje/nje.htm. Norsk entomologisk forening: http://www.entomologi.no/index.htm