Spirulina platensis, a micro algae (cyanobacterium) has been reported as biosorbent for removal of several heavy metals from industrial effluents. The cyanobacterium was exposed to unknown concentration of zinc. Adsorption of heavy metal, namely Zn by the biomass was evaluated under different conditions that included pH, contact time, temperature, concentration of adsorbate and the concentration of dry biomass. The adsorption of heavy metals was found to increase gradually along with decrease in biomass concentration. The biosorption of zinc was estimated as maximum in effluent containing 100 mg of dry biomass for one-liter (0.1 g/L) at pH 8 at 35°C with the optimal contact time of 60 min. The present study describes the Zn absorption by biomass of Spirulina platensis (S. platensis) that has been used to remove many pollutants from effluents by absorption. The process would not only be economic but also eco-friendly and multipurpose as an alternative to conventional methods of biosorption of heavy metals.