Nowadays, wastewater and water treatment with an efficient system for the removal of heavy metals is a serious challenge. Nickel is one of the main heavy metal pollutants that exist in the wastewater of various industries. Several technologies have been developed for removal of nickel, including the new electrochemical processes. In this experimental study, nickel removal by flow-electrode capacitative deionization (FCDI) in batch-mode is investigated. FCDI experiments with water-fed nickel concentrations of 10, 25, and 40 mg/l, input water pH of 5, 6, and 7, and sodium chloride content of 0, 0.1, and 0.2 M in the flow electrode was investigated to achieve the highest nickel removal rate. Finally, the data were analyzed by response surface methodology (RSM). Accordingly, the best nickel removal performance of the system was achieved at pH of about 6.2, electrolyte NaCl concentration of 0.13 M, and input nickel concentration of 10 mg/l.