Air pollution is contemporarily considered to be a significant cause in impairing semen parameters. The aim of this study was to investigate possible effects of traffic pollutants, mainly the diesel exposure, on semen analysis. A total of 38 men working as toll collectors at motorways formed the study group. Simultaneously, 35 men working as office personnel constituted the control group. Factors including varicocele, chronic diseases that can affect sperm production were the exclusion criteria. No difference regarding smoking was present between the groups. Usual semen analysis according to WHO guidelines was performed. The results of semen analysis revealed decreased motility and low sperm counts in eight and seven men from the study group respectively. Besides, a man from the same group had combined abnormality of decreased motility and low sperm count. However, two men from the control group had slight motility defect and one had low sperm count. The differences regarding the abnormal sperm count and motility were significant between the groups (P = 0.002 and P = 0.003, respectively). Similarly, the ratio of sperm cells with normal morphology was significantly lower in the study group than that in the control group (P = 0.001). This observation proposes that air pollution particularly diesel exposure may have detrimental effects on sperm parameters.