An organic light-emitting device includes an organic layer including a carbazole derivative. In the carbazole derivative, a substituent selected from a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group is linked to position 2 of a carbazole group of the carbazole derivative, an amine-based substituent is directly or indirectly linked to position 3 of the carbazole group of the carbazole derivative, and a substituted or unsubstituted C6-C60 aryl group is linked to position 9 of the carbazole group of the carbazole derivative.