An organic light-emitting device includes electrodes and light-emitting units that each include an emission layer; and a charge generation layer, including n- and p-type charge generation layers, disposed between each adjacent pair of light-emitting units. A wavelength of maximum intensity of light emitted from one of the light-emitting units may be different from another, an n-type charge generation layer may have a metal-containing material having a work function of about 2.0 eV to about 4.5 eV, and a p-type charge generation layer may be formed of a hole transport material, an absolute value of a HOMO energy level of the hole transport material being greater than about 5.5 eV, and an absolute value of a LUMO energy level of the hole transport material being less than that of a LUMO energy level of a hole transport layer of a light-emitting unit adjacent to the p-type charge generation layer.