A carbazole-based compound and an organic light-emitting device including the same, wherein the carbazole-based compound is represented by Formula 1: wherein in Formula 1, at least one selected from R1 to R9 may be a group represented by Formula 2, and rings A and B are each selected from a phenyl or a naphthyl. When at least one compound represented by Formula 1 is included as a green fluorescent host in an emission layer of an organic light-emitting device, the example OLEDs may have improved efficiencies and longer lifespans compared to the organic light-emitting devices of the related art.