In the title compound, C(17)H(15)N(3)OS, the phenothia-zine ring system is slightly bent, with a dihedral angle of 13.68 (7)° between the benzene rings. The dihedral angle between the oxadiazole ring and the adjacent benzene ring is 7.72 (7)°. In the crystal, a π-π inter-action with a centroid-centroid distance of 3.752 (2) Å is observed between the benzene rings of neighbouring mol-ecules.