In the title mol-ecule, C16H11BrN2OS, the central imidazo[2,1-b][1,3]benzothia-zole tricycle is essentially planar (r.m.s. deviation = 0.021 Å). The terminal phenyl ring is twisted at 36.18 (5)° from the mean plane of the tricycle. In the crystal, pairs of eak C-H⋯O hydrogen bonds link mol-ecules into centrosymmetric dimers, which are further packed into stacks along the a axis.