Aim: The present study was performed to evaluate the effect of locally delivered Coenzyme Q10 when used as an adjunct to conventional non-surgical mechanical periodontal treatment regarding the periodontal clinical parameters (Primary objective) and the biochemical gingival crevicular fluid levels of IL-1β and IL-10 (secondary objective). Subjects and methods: Thirty periodontitis patients were recruited. Patients were randomly allocated into two groups. Group I (test group) involved fifteen patients who received mechanical periodontal debridement, then single application of 0.2 ml of CoQ10 gel after 48 hours. Group II included fifteen patients who received mechanical periodontal debridement only. Changes in Plaque index, Gingival index, Probing depth, Clinical attachment level, Gingival crevicular fluid IL-1β and IL-10 were assessed after treatment. Results: Regarding CoQ10 effect on GCF level of IL-1β, intergroup comparison of percentage of change after treatment showed significant difference in favor of the test group. The same result was found for IL-10.Conclusion: CoQ10 can be used successfully in conjunction with mechanical plaque control in management of deep pockets in stage II and III periodontitis and could enhance both clinical and GCF biochemical parameters.