The Y-box protein (YP) family shares a nucleic acid binding domain, called cold-shock domain, that has been evolutionarily highly conserved from bacteria to human. The different YPs identified so far in vertebrates are thought to function as transcriptional activators, transcriptional repressors and/or translational repressors. Medakafish and pufferfish are very suitable vertebrate models for the study of developmental genetics and comparative genomics, respectively. Here we report the isolation of two teleost YP genes, medakafish Oryzias latipes (Ola)YP2 and Fugu rubripes (Fru)YP1, which are expressed in multiple tissues. Phylogenetic analysis demonstrated that OlaYP2 and FruYP1 belong to different subclasses of the cold-shock domain protein genes. Future studies in suitable model systems, like the medaka for developmental biology and Fugu for evolutionary genomics, are expected to contribute to our understanding of YPs.