Controlled delivery of antimicrobials directly into periodontal pocket has received eminent interest and holds a level - headed promise in periodontal therapy. Cephalexin, a first generation cephalosporin antibiotic works by interfering with the bacteria's cell wall formation, which ruptures and kills the periodontal pathogen. Thermoreversible pH sensitive in situ gel containing 0.1% w/v cephalexin was formulated by cold method using poloxamer and carbopol polymers. They were evaluated for clarity, pH, gelation temperature, spreadability, drug content, rheological studies, in vitro drug release, invitro anti bacterial activity, and stability studies. All formulations showed satisfactory physico-chemical characteristics. Further, all the formulations showed sustained drug release for a period of 24hours, which is beneficial to treat periodontal infection. The invitro antibacterial study shows that the optimized F3 formulation showed good zone of inhibition against microbial species of anaerobic Porphyromonas gingivalis, gram +ve Staphylococcus aureus and gram –ve Escherichia coli. The results of study indicate that, temperature sensitive poloxamer 407 and pH dependant mucoadhesive carbopol 934 are promising polymers to develop in-situ gel formulation containing cephalexin as a therapeutic agent for treating periodontal disease over conventional therapy. The formulation is stored at 4°C before application, which is syringeable through 21 gauge needles, injected directly into periodontal pocket which immediately converts into gel form at the periodontal temperature and pH.