Lithium-ion capacitors (LICs) are asymmetric electrochemical supercapacitors combining the advantages of high power density and long cycle life of electrical double-layer capacitor (EDLC), and high energy density of lithium-ion battery. A three-electrode LIC cell has been assembled employing activated carbon (AC) cathode and soft carbon anode. Self-discharge behavior and leakage current of LIC cell have been investigated using this three-electrode cell. It has been demonstrated that, in a LIC cell, the constant-voltage charge process and the applied voltage have significant impacts on self-discharge, which mainly occurs on AC cathode. Meanwhile, self-discharge and leakage current of LIC is much superior to EDLC. An approach to diminish self-discharge and leakage current has been proposed accordingly. The results will be beneficial to understand self-discharge behavior of LICs.