The complex of aphelinids and encyrtids (Hymenoptera: Chalcidoidea) parasitizing armored scales (Hemiptera: Diaspididae) on hemlock in Japan (Tsuga diversifolia Masters and Tsuga sieboldii Carrière) and in the eastern United States (Tsuga canadensis [L.] Carrière) was surveyed. Eight new species were discovered and are described here: Five species of Encarsia and one species each of Pteroptrix (Aphelinidae), Coccidencyrtus, and Thomsonisca (Encyrtidae). Two previously known species, Aphytis moldavicus Yasnosh and Encarsia brimblecombei Girault, are recorded for the first time from Japan. New host-parasitoid associations were found for five diaspidids: Fiorinia externa Ferris, Dynaspidiotus tsugae Marlatt, Pseudaulacaspis momi Kuwana, Lepidosaphes japonica Kuwana, and Lepidosaphes pseudotsugae Takahashi.