In the crystal structure of the title compd., C21H13NS3, one of the terminal thiophene rings is disordered in approx. a 3:1 ratio of components, and the disorder is of the flip type. The terthiophene units are far from coplanarity, in contrast to terthiophene itself. The conformation might be described, for the unit of greater occupancy, as quasi-cis [the S-C-C-S torsion angle is 41.1 (5)degrees] quasi-trans [the S-C-C-S torsion angle is -140.1 (4)degrees], and for the less-occupied part as quasi-cis-quasi-cis [35.7 (6)degrees]. The dihedral angle between the terminal ring planes is as high as 71.7 (2)degrees. The central C-C=C-C group is almost planar [max. deviation of 0.027 (3) .ANG.] and it is approx. equally twisted with respect to both the central thiophene and the Ph ring planes [26.5 (4) and 23.5 (7)degrees, resp.]. The crystal packing is detd. by van der Waals interactions, and some weak C-H and C-Hp relatively short directional contacts.