A variety of problems can occur due to the presence of cyanobacteria in water resources used for drinking, agricultural, industrial, commercial, and recreational purposes. In addition, certain cyanobacteria genera are producers of several potent toxins, which endanger the human and animal health. Coagulation is the key step in water treatment process for algae and cyanobacteria, and their associated metabolites removal. The objective of this study was to examine the coagulation processes to optimize the removal of cyanobacterial cells from drinking water under various aluminum sulfate dose and pH values. The influence of cationic polyelectrolyte as a coagulant aid on the cells in accompany with aluminum sulfate was also studied. A set of jar test experiments at 200rpm of rapid mixing, and 30rpm of slow mixing and 30min settling time were conducted to find the optimum chemical dose and pH. From the results of the tests, the optimum dose and pH for aluminum sulfate coagulant and polyelectrolyte were obtained corresponding to the lowest concentrations of cyanobacterial cells and turbidity.