The objectives of this study were to determine the expression and the cellular localization of P450c17 in gonadal tissues in the zebrafish and to investigate the effect of (xeno)-hormones on its expression at both mRNA and protein levels. We showed that gonads are sites for cyp17 gene expression and we documented for the first time the cellular localization of the cyp17 protein expression within ovarian and testicular tissues in a cyprinid fish. Moreover, we demonstrated the down-regulating effect of (xeno)-estrogens on testicular cyp17 expression.