Objective: The aim of this randomized controlled pilot study was to evaluate the effects of indocyanine green (ICG) as an adjunct to nonsurgical periodontal therapy in terms of reduction in percentage of viable bacteria and host tissue injury. Method and Materials: The study included a small cohort of 30 subjects diagnosed with chronic periodontitis. Three sites from three different quadrants were selected and were randomly treated by (1) scaling and root planing (SRP), (2) SRP with application of 810 nm diode laser, or (3) SRP with application of 810 nm diode laser and ICG at a concentration of 5 mg/ mL. Primary parameters included estimation of viable bacteria percentage and lactate dehydrogenase (LDH) levels. Secondary parameters included site-specific measures of plaque, gingivitis, pocket depth (PD), and clinical attachment loss (CAL) at specific time intervals. Results: Sites receiving laser and ICG resulted in a significant decrease in the percentage of viable bacteria at the end of 1 week when compared to the other groups. ICG application does not seem to cause tissue damage as evident by the LDH levels. Comparison of CAL and PD revealed nonsignificant differences in sites treated with laser and ICG at the end of the study period. Conclusion: Laseractivated ICG dye may enhance the potential benefits of SRP and can be used as an adjunct to nonsurgical periodontal therapy. Schlagwörter: antimicrobial photodynamic therapy, bacterial viability, indocyanine green, lactate dehydrogenase, periodontitis, scaling and root planing