The biosorption of nickel from batch solutions and electroplating industrial effluent using cyanobacterium Arthrospira platensis was investigated. The maximum biosorption capacity of nickel was 13.4 mg/g at pH of 4.0, sorbent dosage of 6 g/L during 30 min of contact. The Langmuir and Freundlich adsorption isotherm models fit well the sorption equilibrium of the experimental data (R² 0.99), while the kinetic data were best described using the pseudo second-order kinetic model (R² > 0.99). According to the thermodynamic parameters, the biosorption process was a spontaneous, endothermic process. Fourier transform infrared analysis was carried out to identify the role of different functional groups on cyanobacterium surface in nickel ions binding. According to the data obtained by neutron activation analysis, it has been shown that ion-exchange is one of the mechanism of nickel interaction with biomass. In addition, the effectiveness of the biomass was investigated in three sorption-desorption cycles using HCl, HNO₃, CH₃ COOH and NaOH. In the case of industrial effluent, 68% of nickel was removed from effluent at a sorbent dosage of 20 g/L and interaction time 30 min. The study demonstrates the potential of Arthrospira platensis as biosorbent to remove nickel from batch solutions as well as from industrial effluents.