Background: Plasma glutathione peroxidase (eGPx) is an important selenium containing antioxidant in human defense against oxidative stress. While crevicular fluid (GCF) eGPx levels and its association with periodontal disease is well documented, there is no data on correlation of GCF and serum eGPx levels in chronic periodontitis. Hence this study was undertaken to further probe into the role of oxidative stress in periodontal diseases and effect of nonsurgical periodontal therapy (NSPT) by correlating GCF and serum levels of eGPx.Materials and methods: Thirty subjects (16-Males and 14-Females; age: 30–38 years) participated in the study. The subjects were divided, based on gingival index, probing pocket depth and clinical attachment level into: Healthy (group-1, n=10), Gingivitis (group-2, n=10) and Periodontitis (group-3, n=10). Chronic periodontitis patients after NSPT constituted group 4. GCF and serum samples collected from each subject were quantified for eGPx levels using Enzyme linked Immunosorbent Assay.Results: The mean eGPx concentrations increased from health (14.01 ng/μl and 78.26 ng/ml) to gingivitis (22.86 ng/μl and 90.44 ng/ml) and then to periodontitis (29.89 ng/μl and 103.43 ng/ml), in GCF and serum respectively. After NSPT, there was statistically significant reduction in eGPx concentration in GCF and serum (19.41 ng/μl and 85.21 ng/ml). Further, all the GCF eGPx values showed a positive correlation to that of serum eGPx level.Conclusion: Thus, increased eGPx concentration in GCF can be considered as an indicator of local increase in oxidative stress. While, increase in serum eGPx levels indicates that periodontal disease can also lead to increased oxidative stress at the systemic level.