The Palaearctic species of Ismaridae Thomson, 1858 are reviewed. Thirteen species of Ismaridae are recognized from the Palaearctic. Five species are described as new: Ismarus brevis Kim & Lee sp. nov. from the Russian Far East and South Korea; I. distinctus Kim, Notton & Ødegaard sp. nov. from Norway and the United Kingdom; I. excavatus Kim & Lee sp. nov. from China, Japan and South Korea; I. similis Kim, Notton & Lee sp. nov. from the United Kingdom and I. tripotini Kim & Lee sp. nov. from South Korea. Ismarus apicalis Kolyada & Chemyreva, 2016 is newly recorded from China, France, Japan and South Korea; I. dorsiger (Haliday, 1831) from France, Montenegro, Norway, South Korea and Switzerland; I. flavicornis (Thomson, 1858) from Bulgaria and Norway; I. grandis Alekseev, 1978, I. halidayi Förster, 1850 and I. multiporus Kolyada & Chemyreva from Japan and South Korea; I. rugulosus Förster, 1850 from Austria and I. spinalis Kolyada & Chemyreva, 2016 from China, Japan and South Korea. An identification key to all species found in the Palaearctic region is presented.