Introduction: Periodontitis is inflammation of periodontium that extends beyond the gingiva and produces destruction of the connective tissue attachment of the teeth. It is a complex interrelationship between infectious agents like bacteria and host factors.Aim:To evaluate the adjunctive effects of the photodynamic Therapy using indocyanine green dye to Scaling and Root planing as compared to the conventional mechanical debridement as assessed by clinical parameters in Non–Surgical Periodontal Therapy.Design:30 patients diagnosed as cases of generalized moderate to severe chronic periodontitis based on clinical evaluationwere included in the study. The following clinical parameters were considered to compare both the treatment modalities at baseline and 6 weeks interval Plaque Index (PI), Gingival Index (GI), Sulcus bleeding index, Pocket probing depths (PPD) using UNC–15 probe (Hu–Friedy) and acrylic stent &Clinical attachment levels (CAL) using UNC–15 probe (Hu–Friedy) and acrylic stent.   Results:Significant difference was observed for each variable at both the time intervals (Baseline & 6 weeks) in control and experimental group when analyzed using paired t test. When mean difference (Baseline – 6 weeks) was compared significant difference was observed for all the variables. Conclusion:Scaling and root planning and antimicrobial photodynamic therapy (SRP+APDT) (Experimental group) showed good results then control group i.e scaling and root planning alone (SRP). The present study showed that the addition of single episode of APDT with adjunct to SRP resulted in a significant improvement in terms of PI, GI, SBI, PPD reduction and CAL gain.