Olive flounder Paralichthys olivaceusis an important cultured marine fish. We found that the meiosis marker scp3and its intrinsic regulator dazlwere mainly expressed in the gonads. During the ovarian differentiation, scp3signal was detected first in pre-meiotic oogonia at 60-mm total length (TL) and then in primary oocytes at 80- and 100-mm TL, with a sharp increase in scp3expression level observed at 80- and 100-mm TL. Dazlsignal was detected in primordial germ cells at 30-mm TL and oogonia at 60-mm TL, but no significant change of expression was observed. During the testicular differentiation period, scp3and dazlexpression remained at low levels, and scp3signal was weakly detected in spermatogonia at 80-mm TL, whereas dazlsignal was not found. During the ovarian developmental stages, the highest expression levels of scp3and dazlwere detected at stages I and II, respectively, and strong signals of scp3and dazlwere detected in primary oocytes and oocytes at phases I and II. In the testis, the high expression of scp3and dazlwas detected at stages II–IV and II–III, respectively. Scp3signal was weakly observed in pre-meiotic spermatogonia at stages I and II and strongly detected in primary spermatocytes at stages III–V. Dazlwas detected in the nuclei of spermatogonia and spermatids at stages II–IV. Furthermore, scp3expression in the ovary could be promoted by 17α-ethynylestradiol and tamoxifen, whereas dazlexpression could be downregulated by tamoxifen.The research shows the meiosis begins in the flounder gonads later than the gonadal differentiation.