The effect of oral administration of 50% ethanolic leaf extract of Citrus limon (500 and 1，000 mg/kg body weight/day) for 35 days on fertility and various male reproductive endpoints was evaluated in Parkes strain of mice. Testicular indices such as histology， 3β- and 17β-HSD enzymes activity， immunoblot expression of StAR and P450scc， and germ cell apoptosis by TUNEL and CASP- 3 expression were assessed. Motility， viability， and number of spermatozoa in the cauda epididymidis， level of serum testosterone， fertility indices， and toxicological parameters were also evaluated. Histologically， testes in extract-treated mice showed nonuniform degenerative changes in the seminiferous tubules. Treatment had adverse effects on steroidogenic markers in the testis and induced germ cell apoptosis. Significant reductions were noted in epididymal sperm parameters and serum level of testosterone in Citrus-treated mice compared to controls. Fertility of the extract-treated males was also suppressed， but libido remained unaffected. By 56 days of treatment withdrawal， alterations induced in the above parameters returned to control levels suggesting that Citrus treatment causes reversible suppression of spermatogenesis and fertility in Parkes mice. Suppression of spermatogenesis may result from germ cell apoptosis because of decreased production of testosterone. The present work indicated that Citrus leaves can affect male reproduction.