The use of metformin has significantly increased over the past years in the treatment of many health symptoms. This research investigated the effects of metformin on the reproductive of male sailfin molly fish (Poecilia latipinna) by exposing them to high concentrations of 1320 mg/L (0.08 M) of metformin hydrochloride for different periods and tracking pituitary hormones. The mRNA gene expression and ELISA techniques were used to measure the level of follicle-stimulating hormone (FSH) and luteinizing hormone (LH) hormones. In addition, testis sections were prepared to detect the level of germ cell development in the testis. The Fshb gene expression witnessed an increase after metformin exposure (1.39, 1.63 for T1 and T2, respectively, compared to C: 1.0), whereas Lhb decreased (0.51 and 0.47 for T1 and T2, respectively). ELISA analysis showed increases (T1: 85.99, T2: 104.74, C: 64.23)ng/mL in FSH hormones and decreases (T1: 28.685, T2: 11.535, C: 59.975).ng/mL Metformin effects reflected the development of germ cell stages tending to elevate the number of early stages of sperms but slowing down the mature stages..