An organic light-emitting device having high efficiency and long lifespan including: a first electrode; a second electrode facing the first electrode; and an organic layer between the first electrode and the second electrode and including an emission layer, wherein the organic layer includes a first compound represented by Formula 1 and a second compound represented by Formula 2: When compounds represented by Formulae 1 and 2 are included in the emission layer, organic light-emitting devices may exhibit improved driving voltage, improved luminance, improved efficiency, and/or improved lifespans.