The aim of the study was to optimize the process parameters involved in the green synthesis of silver nanoparticles (AgNPs) by aqueous leaf extract of Tabernaemontana heyneana and to evaluate the catalytic reduction of methylene blue (MB) perhaps for the first time. The various optimum parameters include boiling time for preparation of extract, concentration of extract, silver nitrate concentration, effect of pH, reaction time and temperature were analysed using UV-vis spectrophotometer. The optimized AgNPs were characterized by AFM and evaluated the catalytic activity on reduction of methylene blue. The optimized factors for synthesis of AgNPs were 10 min boiled leaf extract, 3 ml leaf extract addition to reaction mixture, 1 mM AgNO3 concentration, pH 9 of reaction mixture, reaction time 2 h and temperature 80°C. AFM characterization confirmed the oval shaped AgNPs with size 5-20 nm. The synthesized AgNPs showed a good catalytic activity on the reduction of methylene blue. Therefore, it is proposed that, the optimized parameters helps in getting hold of applications in environmental and biomedical sciences.