In the title compound, C17H16N2S, the seven-membered ring adopts a boat conformation. The two aromatic rings are inclined at an angle of 34.7 (1)° to one another. The molecules pack in helical chains running along the c-axis direction through C—H...S hydrogen bonds. These are further linked into layers parallel to (100) by weak C—H...π(ring) interactions. The structure was refined as a two-component inversion twin.