The “Our planet reviewed” expedition allowed to investigate the fish fauna from the Mitaraka Mountain Range (French Guiana). We sampled fishes at 14 sites using complementary sampling methods including rotenone, underwater observation, seine, cast nets, traps and hooks. We present the first detailed fish inventories from this region. Thirty eight species belonging to 16 families were observed, and at least one unknown species belonging to the genus Jupiaba Zanata, 1997 was collected. At two torrential sites we recorded an unusual fish assemblage made of a single Trichomycteridae species, Ituglanis nebulosus de Pinna & Keith, 2003. A few rare species were also recorded such as Pimelodella procera Mees, 1983 hereby extending its known distribution 100 km Southward. Anablepsoides gaucheri (Keith, Nandrin & Le Bail, 2006) was collected for the first time since its description in 2006. This species was collected in a stream located 15 km eastern from its type location, revealing its distribution might span over the entire Mitaraka range. Overall, the species turnover between sites was high even between sites with similar environmental conditions, suggesting that dispersal limitation is playing a significant role in fish assemblage composition. This indicates that complementary inventories in nearby areas may still provide new species and original information on the fish fauna inhabiting small streams of Southern French Guiana.