A new species of the genus Thelohanellus Kudo, 1933 (Myxosporea, Bivalvulida) was isolated from the fins of goldfish Carassius auratus auratus (Linnaeus 1758). The fish had been imported from China by an Austrian retailer. Nodules from the margins of the fins contained pyriform myxospores with a singular polar capsule. In valvular view, the spores measured 12.2 µm in length and 6.4 µm in width. In sutural view, the thickness was 2.9 µm. The polar capsule measured 4.2 × 3.1 µm and contained a polar filament with 8 to 9 coils. Histological sections showed plasmodia of 0.2 to 4.0 mm diameter with the earlier developmental stages of the parasite in the periphery and the mature spores closer to the center. In the transmission electron microscope examination, the different developmental stages could be observed. Morphological data, host specificity, tissue tropism, and molecular analysis of the small subunit rDNA identify this parasite as a new species of Thelohanellus, which we have named Thelohanellus hoffmanni sp. nov.