Plant products have been extensively investigated for their application in the treatment of periodontitis owing to their therapeutic benefits with no major side effects. Further, increasing antimicrobial resistance associated with a constant intake of synthetic antimicrobials has led to a change in paradigm towards the use of phytochemical based formulations as antimicrobial therapy in periodontitis. With this background, our present investigation focuses on developing a novel thermoreversible gel of green tea extract (GT) which is well known for its antimicrobial and antioxidant potential. In the first stage, the antimicrobial activity of GT was assessed against a panel of microbes (S. mutans, P. gingivalis, P. intermedia, F. nucleatum and A. actinomycetemcomitans). Antimicrobial activity of GT extract showed MBC value of 1.25 w/v % with desirable antiadhesion (34–69%) and antibiofilm activity (47–69%). In time kill assay, GT demonstrated time dependent killing varying sensitivity against tested pathogens. In the second stage, based on the MBC value, the thermoreversible gel of GT (GTTG) was formulated using thermosensitive polymer poloxamer 407 (19.5% w/v) and mucoadhesive polymer carbopol 934 (0.4%w/v). Formulated GTTG showed gelation temperature of 29 ± 1 °C, gelation time of 44.67 ± 1.15 s, gelation strength of 45 ± 1 g, the viscosity of 1659 ± 86 cPs and mucoadhesive strength of 1960 dyne/cm2. GTTG showed maximum release and permeation of marker phytochemical Epigallocatechin gallate in 48 and 96 h respectively. Finally, formulated GTTG when compared with gold standard antiplaque agent chlorhexidine gel for its antimicrobial potential showed greater zone of inhibition (ZOI) when tested against key periodontal pathogen P. gingivalis. Hence, the formulated novel GTTG could serve as an effective alternative local drug delivery with ease of administration and accurate dosing for the treatment of periodontitis.