Background: Little is known about Giberellic acid, a plant growth regulator used in many countries, on sperm parameters; so this study was conducted to evaluate its effects on sperm parameters.Materials and Methods: A number of twenty seven adult rats were divided into three groups (n=9): control group (C), control-sham group (C-Sh) and treatment group (Tr). The C-Shgroupand the Tr group were respectively injected 1% methanol and 2mg/kg BW Giberellic acid (dissolved in 1% methanol) intraperitoneally, every other day. On days 15, 30 and 45 three rats from each group were evaluated for sperm parameters including total sperm count, viability (Eosin Negrosin staining), maturity (Aniline Blue staining) and chromatin integrity (using Acridine Orange staining).Results: There was no significant (p<0.05) difference between C and C-Sh groups in any of the parameters. Also no significant (p<0.05) difference between Tr and the other two groups in sperm chromatin integrity and sperm viability but there was a significant decrease in total sperm count of Tr group on day 45 and a significant increase in sperm maturity of this group on days 30 and 45 compared to the other two groups.Conclusion: The longer gibberellic acid is used, the more its detrimental effects on sperm parameters couldtake place.