Objectives: The aim of the present studyis to evaluate the clinical effect of Indocyanine Green photosensitizer activated by Diode laser as an adjunctive treatment to non-surgical periodontal therapy and it's antimicrobial effect on porphyromonas gingivalis and prevotella intermedia  Patients and methods: Thirty patients of both sexes over the age of 30 who were diagnosed with chronic periodontitis were selected. Medical and dental history were taken from the patients. Evaluation of clinical parameters was performed 1. Plaque index. 2. Clinical attachment level. 3 pocket probing depth 4 Bleeding index. The microbiological evaluation was performed by obtaining samples of gingival crevicular fluid. All patients were treated with full scaling and root planing. Then the patients were divided into the two groups: Group 1): consisted of fifteen patients. Application of Photodynamic therapy using diode laser combined with indocyanine photosensitizer. Group 2): consisted of fifteen patients, treated by scaling and root planning. Clinical and microbiological evaluation was performed at the baseline and after six weeks Results: All clinical parameters (PI, SBI, PPD and CAL), total bacterial count in addition to P.gingivalis & P.intermedia counts were revealed statistically significant difference after six weeks of treatment among both groups. However on comparing post-treatment values of P.gingivalis & P.intermedia counts in between groups demonstrated statistically significant difference between groups 1&2. Conclusions: The Indocyanine Green Photodynamic therapy offers a promising therapeutic approach in periodontal treatment as adjunct to SRP.