Aim: The aim of the present split-mouth randomized controlled trial was to assess the effects of antimicrobial photodynamic therapy (aPDT) using toluidine blue dye as an adjunct to scaling and root planing (SRP) on clinical and microbiological parameters compared to SRP alone in patient with localized chronic periodontitis. Methodology: In this split-mouth randomized controlled clinical trial, a total of 13 patients with 26 sites in split-mouth design were used as test and control groups in systemically healthy chronic localized periodontitis patients. The left and right sides were randomly assigned as test and control groups by coin toss method. The test group received aPDT + SRP while the control group received only SRP. Assessment of clinical and microbiological parameters was done at baseline and 3 months posttherapy. The results were subjected to statistical analysis using Statistical Package for the Social Sciences (SPSS) 25, which were expressed as mean ± SD. Results: aPDT as an adjunct to SRP appeared to improve clinical as well as microbiological parameters in localized chronic periodontitis patients. Both the test and control groups showed statistically significant improvement from baseline to 3 months, but the test group (aPDT + SRP) showed better results than the control group (SRP). Conclusion: Within the limitations of this present split-mouth randomized controlled clinical trial, results indicate that aPDT can be an effective adjunct to SRP in the treatment of shallow to moderately deep periodontal pockets. aPDT + SRP showed appreciable improvement in reduction of Porphyromonas gingivalis and Fusobacterium nucleatum colony-forming units (CFU)/mL in test groups at 3 months follow-up.