The green alga Prasiola fluviatilis (Sommerfelt) Areschoug ex Lagerstedt occurs in cold lotic environments. The species has a mainly circumarctic distribution, but has also been reported from glacier areas in lower latitude regions in both hemispheres. It was reported from China on a single occasion in the first half of the 20th century, but without description, illustrations or voucher specimens the identity of this record cannot be verified. Here we confirm the presence of P. fluviatilis in the Tianshan Mountains, Xinjiang Province, China based on morphological features, habitat characteristics, and plastid rbcL and tufA gene sequences. The biogeographic distribution of P. fluviatilis and its phylogenetic relationship with other terrestrial and freshwater Prasiola species are discussed.