In the title compound, C12H9ClN2S, the imidazo[2,1-b]thia-zole fragment is planar (r.m.s. deviation = 0.003 Å), and the benzene ring is twisted slightly [by 5.65 (6)°] relative to this moiety. In the crystal, mol-ecules are linked by π-π stacking inter-actions into columns along [010]. The mol-ecules within the columns are arranged alternatively by their planar rotation of 180°. Thus, in the columns, there are the two types of π-π stacking inter-actions, namely, (i) between two imidazo[2,1-b]thia-zole fragments [inter-planar distance = 3.351 (2) Å] and (ii) between an imidazo[2,1-b]thia-zole fragment and the phenyl ring [inter-planar distance = 3.410 (5) Å]. There are no short contacts between the columns.