Objective: The present study aimed to assess the adjunctive use of Hyaluronic acid with scaling & root planing (SRP) in patients with chronic periodontitis & diabetes mellitus type 2. Subjects &Methods: Thirty subjects with chronic periodontitis & diabetes mellitus type 2 were included in this randomized clinical trial. These subjects were randomly allocated into test & control equal groups. The test group comprised fifteen patients who received SRP with subgingival application of Hyaluronic acid as an adjunct. The control group included fifteen patients who received SRP alone. Plaque index (PI), gingival index (GI), probing depth (PD) & clinical attachment level (CAL) were measured & documented at baseline, 6 weeks & 12 weeks intervals. Results: A statistically significant clinical improvement in all clinical parameters was shown in the test & control groups after SRP, 6 weeks & 12 weeks follow up intervals (p≤0.05). Statistically significant better results were observed in the test group, compared to control group, in all periodontal parameters, except PI, at 6 weeks and 12 weeks (P≤0.05). Conclusion: Adjunctive use of Hyaluronic acid with SRP in the treatment of chronic periodontitis patients with diabetes mellitus type 2 offers superior clinical results compared to SRP alone.