An organic light-emitting device including a first electrode, a second electrode facing the first electrode, an emission layer between the first electrode and the second electrode, a hole transport region between the first electrode and the emission layer, and an electron transport region between the emission layer and the second electrode; wherein the electron transport region comprises at least one first compound, the emission layer comprises at least one second compound, the first compound is represented by Formula 1, and the second compound is represented by one selected from Formulae 2-1, 2-2, and 2-3: