The taxonomy of marine ostracod assemblages from Belca section in the Karavanke Mountains, northwestern Slovenia, is discussed, adding to the scientific understanding of marine ostracods during the Carnian stage, Late Triassic. In Belca, the ostracod assemblages include 39 species, among which two are newly described: Dicerobairdia buseri Forel, n. sp. and Pontocypris? karavankensis Forel, n. sp. The recovery of abundant juvenile and adult specimens facilitated the illustration and discussion of the ontogenetic series of several typically Triassic species including Renngartenella sanctaecrucis Kris-tan-Tollmann inKristan-Tollmann & Hamedani, 1973, Leviella bogschiKozur, 1972 and Leviella veghaeKozur, 1972. The occurrence of sexual dimorphism is furthermore confirmed for Renngartenella sanctaecrucis. Ostracods in Belca record a major shift from low diversity and high dominance assemblages at the base of the section to higher diversity and lower dominance with diversification of stable open-marine taxa in the upper part. This pattern might illustrate low salinity levels related to high land-derived input at the base of the section and a return to relatively normal marine salinity in the intermediate sublittoral zone in the upper portion of Belca section.