In the title compound, C16H15NO2S [alternative name: rac-2,3-diphenyl-1,3-thia-zinan-4-one 1-oxide], the thia-zine ring exhibits an envelope conformation, with the S atom forming the flap. The sulfoxide O atom is in a pseudo-axial position on the thia-zine ring and is trans to the phenyl group on C-2. The phenyl rings form a dihedral angle of 89.47 (19)°. In this racemate crystal, homochiral mol-ecules form slabs parallel to (010) of thickness b/2 which then stack with alternating chirality in the b-axis direction. The stacking is aided by edge-to-face inter-actions between the phenyl rings of racemic mol-ecules. Within each of the single-enanti-omer slabs, the mol-ecules are held by C-H⋯O-type inter-actions, with an H⋯O distance of 2.30 Å, forming infinite chains along the c-axis direction, as well by the edge-to-face inter-actions between phenyl rings of neighboring mol-ecules in the a-axis direction.