Introduction and objectives: Around 15% of productive couples in the world are infertile. Recent years, biochemical mechanisms leads to male infertility are started to research. Redox regulation and oxidative stress (OS) show importance in the pathogenesis of infertility in male. Malondialdehyde (MDA) and Glutathione (GSH) are biochemical indicatives of sperm damage by reactive oxygen species (ROS). In addition, sperm are coated with a thick glycocalyx rich in sialic acids. It is aimed to determine and evaluate the differences between normozoospermic and oligozoospermic individuals according to sialic acid, MDA and GSH concentrations and correlations between spermyogram and these parameters. Material and methods: This study was carried out on seminal plasma of individuals who admitted to Selcuk University Faculty of Medicine IVF Unit Andrology Laboratory. The groups were divided into two as normozoospermics (n = 30, sperm concentration ≥ 15 million/mL), and oligozoospermics (n = 30, sperm concentration < 15 million/mL). Spermyogram were evaluated regarding WHO (2010) Kruger criteria. GSH, MDA and sialic acid concentrations were analyzed in seminal plasma. Diagnostic performance of sialic acid has been determined with ROC curve analysis. Results: Sialic acid levels were significantly lower in Normozoospermic than Oligozoospermic individuals (p < 0.0001), MDA and GSH levels were not differ significantly in both groups (p > 0.05). Sialic acid correlated significantly with most of the spermyogram findings. When diagnostic performance of sialic acid was evaluated, the cut off value of sialic acid found as 4.175 nmol/mL by ROC curve. Conclusion: High seminal plasma sialic acid levels may be used as a biomarker and sialic acid is important determinant in oligozoospermia.