Ostracod assemblages of the Upper Permian Bellerophon Formation at Seis near Bozen (South Tyrol, Italy) have been studied with respect to their taxonomy and palaeoecology. The investigations were concentrated on the Late Changsingian Casera Razzo Member which yielded five ostracod assemblages including more than twenty-four species. Twelve of these species are described herein and four species are new, including two species with strong affinity to taxa appearing in the Early Triassic. The lithofacies characteristics and low species diversity are suggestive of a protected shallow lagoonal environment with salinity fluctuations due to freshwater influx. Only four species are recorded from Late Permian localities outside of the Dolomites. This is due to the restricted environmental conditions which inhibited the immigration of more taxa from open shelf environments.