An organic light-emitting device includes a first electrode, a second electrode, and an organic layer between the first electrode and the second electrode. The organic layer including an emission layer. The emission layer includes a first host represented by Formula 1 and a second host represented by Formula 2. A volume ratio of the first host to the second host is in a range of about 94:3 to about 77:20: where R11 to R14, R21, R23 to R26, L11, L21, L23, X21, a11, a21, a23, b11 to b14, b21, and b23 to b26 are as defined in the specification.