An organic light-emitting device and an apparatus including the same are disclosed. The organic light-emitting device includes: 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 includes an emission layer, the emission layer includes a first compound, a second compound, a third compound, and a fourth compound, the first compound is represented by Formula 1, the second compound is represented by Formula 2, the third compound is represented by Formula 3, the fourth compound is represented by any one of Formulae 4-1 to 4-3, each as respectively described in the detailed description.