Abstract: Celery (Apium graveolens) has many therapeutic effects. This plant has many phytoestrogens that can affect on the reproductive endocrine system and can reduce fertility. In this study, hydro alcoholic extracts of celery leaves on the reproductive parameters in young male mice of Balb/C was investigated. The samples were randomly divided into 5 groups (3 treatment groups, placebo and control). Celery leaves hydro-alcoholic extract in different doses (50, 100, 150 mg/kg/2 day) was injected (IP) for 20 days. The placebo group was used for injection of normal saline. The samples were randomly divided into 5 groups (3 treatment groups, placebo and control). After 10 injections, samples bloods were analyzed for FSH, LH and testosterone using RIA method. Results showed that concentrations of FSH in 100 and 150 mg kg^-1 decreased significantly while LH and testosterone concentrations in all experimental groups decreased (p<0.05). This study showed dose dependent negative effect of celery extracts in male reproductive potential.