The title mol-ecule, C12H12N2OS, is planar, with an r.m.s. deviation of 0.04 Å. In the crystal, the N atom adjacent to the carbonyl group is sp (2)-hybridized. The crystal structure is stabilized by π-π stacking inter-actions observed between thio-phene and pyrimidinone rings of c-glide-related mol-ecules [centroid-centroid distance = 3.9554 (13) Å] and by C-H⋯π inter-actions, forming an infinite chain along the c-axis direction.