Functions of the relaxin peptide family have been primarily investigated in mammals, and little attention has been paid to nonmammalian species. In this work, we performed phylogenetic and syntenic data analyses to identify the number and orthologous and paralogous relationships of relaxin family genes in teleosts and humans. Additionally, we performed reverse transcription PCR to determine the expression of three members of the relaxin family in zebrafish brain and gonads. We found evidence that teleosts harbor orthologs of the human INSL5, H2, H3, and INSL3 genes, so-named RLND/RLNE, RLNC, RLN3a/RLN3b, and RLNF in teleosts, respectively. Moreover, the presence of mRNA for RLN3a, RLND, and RLNF in both male and female brain and gonads of zebrafish suggests that all three genes are expressed in these tissues of this teleost. Differential expression and/or regulation of these genes will be explored in future experimental work.