Background: Varicocele is one of the most common reasons for male infertility and could impair spermatogenesis through mechanisms that are not well known. Recently, oxidative stress has been introduced as a major reason for male infertility caused by varicocele.Objectives: In the current study, we aimed to assess the TAC (total antioxidant capacity) and MDA (MALONDIALDEHYDE) as stress oxidative markers in infertile men with varicocele and fertile men, and moreover, their correlation with sperm parameters.Patients and Methods: This case control study was performed on 43 infertilemen with varicocele and 46men with proven fertility.The ferric reducing ability of plasma (FRAP) and thiobarbituric acid (TBA) reaction methods were used for seminal plasma TAC and MDA assay, respectively.Results: Lower TAC levels (1.70.2 vs.1.30.4 mmol/L, P=0.0004) and higherMDAlevels (2.51.1 vs.5.81.9 mmol/L, P<0.0001) were observed in infertile men with varicocele compared to fertile men. There was no correlation between TAC and MDA in fertile men (r=0.02, P=0.9), however, a negative correlation was found between TAC andMDAlevels in varicocele infertilemen (r=-0.44, P =0.003). Moreover, a positive correlation was found between sperm count and sperm motility with TAC levels in varicocele infertile men (r=0.4, P=0.02 and r=0.6, P<0.0001, respectively). There was a correlation between sperm motility and TAC levels in fertile men (r=0.5, P=0.001), but other parameters did not correlate with TAC in this group. A negative correlation was shown between semen volume, sperm count, total sperm, sperm motility, and sperm morphology with MDA levels in varicocele infertile men (r= 0.3, P=0.045; r=-0.4, P=0.009; r=-0.5, P=0.002; r=-0.5, P=0.001 and r=-0.4, P=0.008, respectively). There was no correlation between these parameters and MDA in fertile men.Conclusions: Our findings indicated that oxidative stress could play an essential role in male infertility caused by varicocele and may impair spermatogenesis leading to infertility.