Eco-friendly anti-algal agents are in demand for preventing the growth of unwanted algae. Green synthesized nanoparticles exhibit antimicrobial properties and have been used as a better alternative against chemical and physical processes. In the present study, treatment of silver nitrate with leaf extracts (5% w/v) of Tinospora cordifolia, a plant with proven antimicrobial effects, exhibited UV-visible absorption maxima between 440-460 nm after 1h indicating bioreduction of silver to nanoparticles. The green synthesised silver nanoparticles (5 mgl-1) exhibited inhibition zones against Chlamydomonas reinhardtii in in vitro agar assays. Treatment with green synthesised silver nanoparticles during exponential phase of algal growth resulted in significant reduction in algal population, carbohydrate, protein and chlorophyll contents confirming the anti-algal potential. This is the first report on the growth inhibitory potential of green synthesised silver nanoparticles against green algae.