In the title compound C13H11NS, the phenothiazine unit has a non-planar butterfly structure, and the central six-membered ring adopts a boat conformation. The dihedral angle between the two outer aromatic rings of the phenothiazine unit is 39.53 (10)°. In the crystal, a π–π interaction with a centroid–centroid distance of 3.6871 (12) Å is observed between the aromatic rings of neighbouring molecules.
