Recently discovered interleukin 29 (IL-29) has antiviral properties and its production is induced by herpes viruses. This study was aimed at analyzing the effect of non-surgical periodontal treatment on IL-29 levels in gingival crevicular fluid (GCF) of chronic and aggressive periodontitis patients. A total of 60 participants were divided into healthy group (group 1; n = 20), chronic periodontitis group (group 2; n = 20), and aggressive periodontitis group (group 3; n = 20). GCF samples collected from each subject at baseline and 6–8 weeks after scaling and root planing were quantified for IL-29 levels using ELISA. The mean IL-29 concentration in GCF was found to be highest in group 3 (92.37 pg/μl). The mean IL-29 level in group 1 and group 2 was 36.88 pg/μl and 69.35 pg/μl respectively. After scaling and root planing, the mean concentration of IL-29 in GCF was increased to 85.99 pg/μl in group 2 and to 114.64 pg/μl in group 3. Results of the present study indicate that antiviral IL-29 level was highest in GCF of aggressive periodontitis patients and least in subjects with healthy periodontium, while that of chronic periodontitis lying in between. After non-surgical periodontal therapy, IL-29 levels increased both in chronic and aggressive periodontitis patients and deserve further investigation as a potential therapeutic agent in treating periodontitis.