Tea tree oil (TTO) is known to have antimicrobial, antifungal, antiviral, antioxidant, and anti-inflammatory effects. Periodontitis, chronic inflammation of the supporting tissues of the teeth leading to loss of the periodontal ligament and bone, results in disruption of the balance between periodontopathic bacteria and the host response to these microorganisms. We tried to evaluate the effects of TTO alone and in combination with scaling and root planning (SRP) in a triple-blind, randomized controlled clinical trial of volunteers with chronic periodontitis. Thirty systemically healthy, chronic periodontitis patients were included.The study period was 21 days and the "splitmouth" design was used. Tea tree oil films were inserted in the selected pockets on day 0, removed, and reinserted on day 7. Statistical analysis was done for comparisons of clinical parameters [plaque index (PI), gingival bleeding index (GBI), probing pocket depth (PPD), clinical attachment level (CAL), and microbiological levels of the pathogens Porphyromonas gingivalis and Prevotella intermedia. Tea tree oil could serve as a useful adjunct or alternative to periodontal treatment.