In the title compound, C20H14F3NS2, the seven-membered thia-zepine ring adopts a slightly distorted twist-boat conformation. The mean plane of the five-membered thio-phene ring fused to the thia-zepine ring is twisted by 32.3 (3) and 55.6 (4)° from the benzene and phenyl rings, respectively. In the crystal, inversion dimers linked by pairs of weak C-H⋯N inter-actions are observed.