In the title mol-ecule [systematic name: 10-(prop-2-yn-1-yl)dipyrido[3,4-b:3',4'-e][1,4]thia-zine], C(13)H(9)N(3)S, the dihedral angle between the two pyridine rings is 146.33 (7)° and the angle between two halves of the thia-zine ring is 138.84 (8)°, resulting in a butterfly shape for the tricyclic system. The central thia-zine ring adopts a boat conformation, with the 2-propynyl substituent at the thia-zine N atom located in a pseudo-equatorial position and oriented to the concave side of the diaza-phenothia-zine system. In the crystal, mol-ecules are arranged via π-π inter-actions between the pyridine rings [centroid-centroid distances = 3.838 (1) and 3.845 (1) Å] into stacks extending along [001]. There are C-H⋯C and C-H⋯N inter-actions between mol-ecules of neighbouring stacks.