Titanium dioxide is a nanoparticle which is widely used as a sanitary compound to control microorganis ms. Small size of this particle, chemical compound and high r eactivity may cause potential risks for human or en vironment. This research was carried out to study the effects of titanium dioxide nanoparticles on pituitary-test icular axis of male Syrian mice. Forty mature male mice were divid ed in four groups. Control group, placebo group did not receive any treatment except ordinary food and wate r. Experimental groups received 10 and 100 ppm of t itanium dioxide nanoparticles via gavage for 14days. At the end of the experiment, mice were anesthetized with chloroform, blood samples were taken from the heart and LH, FSH and testosterone hormones were measured using stan dard tests. Results showed that LH, FSH, and testosteron e concentrations were decreased significantly in pr oportion to control group (p<0.05).Therefore, titanium dioxide reduces pituitary-testicular axis hormones and decr eases reproductive potential of male sex.