The simultaneous process of NaOH production via electrolysis of NaCl and CO2 capture was investigated due to the expectation of reduction in capital cost. It was found that seawater concentration of NaCl solution was adaptable to be used as both anolyte and catholyte and that 90 degrees C was the most proper temperature for NaOH production among the test conditions in this work. Under these electrolyte and temperature conditions, the simultaneous NaOH production and CO2 capture processes were conducted and more than 98.83% of OH- was reacted with CO2 to yield aqueous carbonate solutions. Additional electrochemical CO2 capture tests were carried out depending on the different CO2 concentration of mixed gases.