AbstractBackgroundThe marine gastropod molluscNassarius sinarumhas attracted attention due to its status as a potential invasive species and the ecological impact it may have on local environments and the fishing industry. It was observed exclusively within China initially, but its distribution now seems to have expanded into Japan and Korea. Accurate identification ofN. sinarum, particularly in its juvenile stage, is vital for understanding its ecological influences and distribution patterns.New informationThis study represents the first comprehensive analysis ofN. sinarumsamples from Korea. It includes morphological examination, scanning electron microscopy images and molecular sequencing. Two live specimens were collected from the Yeongsan River estuary in Korea and their morphological features were analysed and compared to those of samples from China and Japan. The samples’ species were confirmed by molecular identification, based on cytochrome c oxidase subunit I (COI) and histone H3 (H3) genetic markers.It was observed that juvenileN.sinarumshells lack key species-characteristic morphological traits, such as a thick outer lip and diminishing axial ribs. However, COI marker-based molecular identification affirmed that these Korean specimens wereN. sinarum. The H3 region was registered with the National Center for Biotechnology Information (NCBI) for the first time. Phylogenetic analysis of the H3 region did not resolve species distinctions within theNassarius, suggesting that the H3 marker is not suitable for species identification within this genus. In this context, multiple genetic markers, when used appropriately, can also be applied to genus-level searches, enhancing species identification accuracy and reducing misidentification.The sequences provided in this study can serve as a valuable reference for future DNA barcoding research. Additional samples and surveys should be conducted through collaborative efforts amongst national and institutional organisations to further clarify the ecological status ofN. sinarumand to investigate its distribution and potential impact around East Asia. Finally, a new Korean name, (No-lan-jul-job-ssal-mu-nui-go-dung; 노란줄좁쌀무늬고둥) has been proposed forN. sinarum.