The title compound, C(15)H(13)ClN(2)O(3)S, is one of a series of N(1)-benzyl-1,3-dihydro-2H-benzimidazol-2-one derivatives, a new class of non-nucleoside HIV-1 reverse transcriptase inhibitors. The dihedral angle between the two pharmacophoric groups, the dimethyl-benzene ring and the benzimidazolone ring system, is 88 (1)°, giving a butterfly-like conformation to the mol-ecule. The mol-ecular packing is characterized by a bifurcated N-H⋯(O,O) hydrogen bond and short Cl⋯O contacts of 3.122 (2) Å. In addition, π-π stacking of the benzimidazolone rings is also present, with inter-planar separations of 3.95 (1) Å.