Male urogenital tract infection plays an important role in men infertility. Asymptomatic bacteriospermia has been paid attention as a major cause of male infertility. The aim of this study was to microbiological investigation of semen sample of infertile men attending to infertility clinic and evaluation of the effects of bacteriospermia on semen quality. Eighty eight infertile men were evaluated by standard bacterial culture method. Standard semen analysis was performed according to WHO guidelines. Among total cases, 35.22% (31 cases) showed at least one pathogen: 10.22% E.coli, 9.09% Coagulase Negative Staphylococci (Saprophyticcus), 6.81% Group B Streptococci, 5.88% Entrococci, 5.68% Candida sp., 2.27% Gonococci, 2.27% Staphylococcus aureus, 1.13% Klebsiella sp. and 1.13% Providencia sp. There was a significant relation between the bacteriospermia and the rate of no motile and morphologically abnormal sperms (P<0.0001). The quality of sperm motility was significantly decreased in contaminated semen. The percentage of morphologically normal sperm was lower. E.coli and Entrococci were the most effective agents against sperm parameters. Asymptomatic bacteriospermia has a negative effect on sperm quality. E.coli and Entrococci are the most common bacteria with negative influence on sperm motility and morphology. Moreover, presence of bacteriospermia and leukocytospermia did not correlate with each other (P>0.05). It seems that leukocytospermia is a poor marker to predict bacteriospermia.