Green tea extract is a naturally occurring antimicrobial agent, consisting of polyphenols (catechin) with anticariogenic, anti-inflammatory, anticollagenolytic properties. Hence, in the present study, an attempt was made to develop a thermo-reversible sustained-release green tea gel and to study its clinical effects on patients with chronic periodontitis (CP). Thermo-reversible sustained-release green tea catechin gel was prepared and tested for its in vitro release characteristics. An in vivo controlled, randomized, split-mouth single-evaluator masked study was conducted. Thirty patients with two sites in the contralateral quadrants having probing depths (PDs) of ≥4 mm were selected. Assessment of gingival index (GI), PD, and relative clinical attachment levels (rCALs) was done at baseline and at 4 weeks. Green tea and placebo gels were placed at test and control sites as an adjunct to Phase 1 periodontal therapy. Comparison of the mean ± SD GI, PD, and rCAL values within the test group at baseline (1.92 ± 0.24, 4.93 ± 0.58, and 9.97 ± 0.72, respectively) and the end of 4 weeks (0.01 ± 0.04, 2.87 ± 0.51, and 7.87 ± 0.51, respectively) showed high statistical significance (P <0.001). Comparison of mean ± SD of GI, PD, and rCAL within the control group at baseline (1.95 ± 0.16, 4.77 ± 0.50, and 9.73 ± 0.45, respectively) and the end of 4 weeks (0.16 ± 0.11, 3.8 ± 0.48, and 8.76 ± 0.43, respectively) showed significance with P <0.001. High significance was observed between the delta of measurements (0 to 4 weeks) of GI, PD, and rCAL between test (1.91 ± 0.20, 2.06 ± 0.07, and 2.1 ± 0.21, respectively) and control (1.79 ± 0.05, 0.97 ± 0.02, and 0.97 ± 0.02, respectively) groups. Adjunctive local drug therapy with thermo-reversible green tea gel has shown to reduce pockets and inflammation during the 4 weeks of the clinical trial in patients with CP.