Species diversity of Ichneumonidae (Hymenoptera) is studied in the province Mazandaran (northern Iran). In total, 27 species from 22 genera were collected and identified. The subfamily Oxytorinae Thomson, 1883 and the genus Agrypon Förster, 1860 are new records for the fauna of Iran together with eight species: Agrypon clandestinum (Gravenhorst, 1829), Lissonota (Lissonota) nitida (Gravenhorst, 1829), Meloboris collector (Thunberg, 1824), Gelis agilis (Fabricius, 1775), Gelis stevenii (Gravenhorst, 1829), Lathrolestes buccinator (Holmgren, 1857), Oxytorus luridator (Gravenhorst, 1820) and Polyblastus (Polyblastus) cothurnatus (Gravenhorst, 1829). In this paper, five species are recorded for the first time as the hosts of Ichneumonidae: Lacanobia oleracea (Linnaeus, 1758) (Lepidoptera: Noctuidae) for Meloboris collector (Thunberg, 1824), Apterona helicoidella (Vallot, 1827) (Lepidoptera: Psychidae) for Cryptus spiralis (Geoffroy, 1785), Fenusa ulmi Sundevall, 1847 (Hymenoptera: Tenthredinidae) for Lathrolestes buccinator (Holmgren, 1857), Hedya nubiferana Haworth, 1811 (Lepidoptera: Tortricidae) for Exochus castaniventris Brauns, 1896 and Leucoma wiltshirei Collenette, 1938 (Lepidoptera: Erebidae) for Aritranis director (Thunberg, 1824).