An organic light-emitting device including a first electrode; a second electrode facing the first electrode; and an organic layer between the first electrode and the second electrode, the organic layer including an emission layer, a hole transport region between the first electrode and the emission layer, the hole transport region including at least one selected from a hole transport layer, a hole injection layer, and a buffer layer, and an electron transport region between the emission layer and the second electrode, the electron transport region including at least one selected from a hole blocking layer, an electron transport layer, and an electron injection layer, wherein the emission layer includes a compound represented by Formula 1 as described herein; and at least one of the hole blocking layer, the electron transport layer, and the electron injection layer in the electron transport region includes at least one compound represented by Formulae 2, 3, 4, or 5, as described herein.