An organic light-emitting device is provided. The organic light-emitting device includes: a first electrode; a second electrode; 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; and an electron transport region between the emission layer and the second electrode, 50% or more of a total volume of the second electrode being silver (Ag), the hole transport region including an amine-based polymer including a first repeating unit represented by Formula 1, and a number average molecular weight of the amine-based polymer being about 1,000 or more.