Objective: The Aim of the Study is evaluation of the effect of locally delivered melatonin as an adjunct to non surgical periodontal therapy on the GCF level of DKK1 in smokers with chronic periodontitis.Materials and methods: This study was conducted on 30 patients divided into two groups. Group I (intervention): consisted of 15 subjects with a minimum of 2 sites of probing depth ≥ 4 mm undergone full mouth scaling and root planning debridement with topical application of melatonin inside the pocket. Group II (control): consisted of 15 subjects which have undergone full mouth scaling and root planning without topical application of melatonin. GCF sample was collected (before and after 3 months) from all groups for assessment of DKK1 level in GCF and clinical parameters.Results: It was shown that there is a significant difference between intervention group(SRP + topical application of melatonin) and control group(SRP alone) regardening improvement in clinical parameters and decrease in GCF level of DKK1 after treatment with favors to the intervention group in chronic periodontitis patients. Conclusion: melatonin exert a beneficial effect on decreasing periodontal inflammation, suggesting that that topical administration of melatonin can be used as an adjunct to conventional treatment protocols such as scaling, root planning, to improve the outcomes of periodontal therapy.