In the title compound, C(17)H(16)N(2)O(2)S, the pyrazinone ring is non-planar (r.m.s. deviation = 0.1595 Å), with maximum deviations for the 4-position N atom and the adjacent non-fused-ring C atom of 0.2557 (15) and -0.2118 (16) Å, respectively. The dihedral angle between the benzyl ring and pyrazinone rings is 30.45 (18)°. Inter-molecular N-H⋯O hydrogen-bonding inter-actions forms inversion dimers which lead to eight-membered R(2) (2)(8) ring motifs. The dimers are further connected by C-H⋯O inter-actions.