Background:The aim of this study was to compare the efficacy of injectable form of PRF to antimicrobial photo dynamic therapy as an adjunctive treatment to non-surgical periodontal therapy in patients with stage III grade B periodontitis in terms of clinical improvement and antimicrobial ability.Subjects and Methods: 39 patients of each gender with age vary from 30 to 60 years diagnosed with stage III grade B periodontitis. The patients were divided randomly into three groups. (Group I) 13 patients treated by SRP (scaling and root planning) with application of i-PRF, (Group II) 13 patients treated by SRP with application of 940 nm diode laser and Indocyanine green (ICG), (Group III) treated by SRP alone as a control group. Clinical parameters such as GI (gingival index), PI (plaque index), CAL (clinical attachment level) and PD (probing depth) were recorded preoperatively and 3 months post operatively. Site-specific measure of bactericidal effect against Pg (Porphyromonas gingivalis) preoperative, 1 week postoperative and 1 month postoperative for all groups.Results: group I who receiving i-PRF resulted in a significant decrease in the percentage of Pg at the end of 1 month when compared to the other groups. Comparison of clinical parameters revealed significant differences in patients treated with aPDT in relation to GI, and CAL while i-PRF group , was better in PD at the end of the study period. Conclusion:i-PRF and aPDT may enhance the potential benefits of SRP in periodontitis patients and can be used as an adjunct to nonsurgical periodontal therapy.