The removal of heavy metal ions by microorganisms may present an alternative method for their removal from wastewater. In this study, 10 cyanobacteria were isolated from Kucukcekmece Lagoon (Turkey). All the isolates were examined for nickel(II) concentrations in the range of 5-25 mg/L. EC50 values of the isolates were determined by probit analysis. Synechocystis sp. BASO403 (EC50 of 17.41 mg/L) and Synechocystis sp. BASO404 (EC50 of 2.56 mg/L) were selected among the isolates based on their capacity to produce extracellular polysaccharides (EPS; 143 mg/L and 44 mg/L), respectively, for removal at 15 mg/L Ni(II) concentration. The BASO404 isolate displayed a higher Ni(II) removal (95%), especially on the cell surface, than BASO403 (51%) after a 7-days incubation period. A reverse relationship between EPS capacity and Ni removal (p<0.01) was indicated, but a positive correlation was observed between EPS capacity and Ni toxicity (p<0.01). It is suggested that EPS from two isolates of Synechocystis sp. play a protective role for Ni(II) toxicity.