The cyanobacterium Spirulina platensis, widely used for physiological, biochemical, genetical, biotechnological, and ecological purposes, was used to study the process of silver biosorption. The biosorbent was characterized by scanning electron microscopy, multi-element neutron activation analysis and FTIR analyses. The optimal biosorption conditions were determined as pH 3.0, biosorbent dosage of 0.4 g, and initial silver concentration of 25 mg/L. Equilibrium adsorption data were analyzed by the Langmuir and Freundlich models. The Freundlich model provided a better fitting with the experimental data in comparison with the Langmuir one. The kinetic data fitted well into the pseudo-second-order model with correlation coefficient 0.99. FTIR spectra have indicated that the metal removal takes place through binding to OH, C=O, and NH2 groups. Spirulina platensis biomass can be applied for silver biosorption from wastewater. The biosorption capacity of biomass Spirulina platensis serves as a basis for the development of green technology for environmental remediation.