Objective: Chronic periodontitis (CP) is a common inflammatory disease that causes destruction to the supporting tissues of the teeth. Many treatment modalities tried to stop the disease progression. Platelet-rich plasma (PRP) is one of the regenerative methods that used in adjunct to conventional periodontal treatment. The aim of this study was to evaluate the anti-inflammatory effect of PRP by monitoring the lymphocyte count before and after its application to the periodontal pocket. Materials and Methods: Twenty patients, with CP and a pocket depth equal to or deeper than 4 mm, subjected to scaling, root planing, and PRP injection into the pocket. The lymphocyte count measured before and after 1 month from PRP application. Clinical periodontal parameters were taken during two visits (1 month apart), with customized stent fabrication. Results: All clinical periodontal parameters showed a reduction in their value following 1 month of PRP application. . There was a noticeable reduction in lymphocyte count from (mean 2.47 ± 0.91) to (mean 1.94 ± 0.77). Conclusion: In addition to its traditional uses, PRP has a great role in the periodontal treatment by its anti-inflammatory effect.