The non-marine ostracod fauna from the Xiaonangou Formation in the Baishan Basin is described in detail and illustrated for the first time. Eight samples from the Guanghuanjie-Yumuqiaozi section were analyzed, and seven taxa were praevara, Candonidae gen. indet. sp. and Cyclocypris invalida. This comprehensive taxonomic study not only enhances our understanding of Cretaceous non-marine ostracods in China but also provides the first precise age constraint for the Xiaonangou Formation using ostracod biostratigraphic correlation. Based on ostracod biostratigraphic correlation, the age of the Xiaonangou Formation has been identified as early Albian. Additionally, this study supports the hypothesis of invertebrate faunal exchange in northeastern China during the Early Cretaceous.