An organic light-emitting device including a first electrode, a second electrode facing the first electrode, and an organic layer disposed between the first electrode and the second electrode, wherein the organic layer includes an emission layer, wherein the an emission layer including an auxiliary dopant, a fluorescent dopant, and a host, wherein the auxiliary dopant includes a compound represented by Formula 1, and wherein the fluorescent dopant emits prompt fluorescence: wherein in Formula 1, groups and variables are the same as described in the specification.