In the title compound, C11H10ClN3S, the dihedral angle between the benzene and pyrimidine rings is 3.99 (4)°. In the crystal, intermolecular N—HN hydrogen bonds link the molecules into ribbons of R 2 2(8) rings parallel to . Weak C—HS contacts connect adjacent ribbons into a two-dimensional undulating layer-like structure extending parallel to (110). The benzene and pyrimidine rings of adjacent molecules have the offset face-to-face π–π stacking interactions in a zigzag fashion along the c axis, with perpendicular ring distances of 3.463 and 3.639 Å, and a dihedral angle between the planes of 3.99 (2)°. The distance between the ring centroids is 4.420 (2) Å.