The title compound, C18H16N2O3S, was synthesized by reaction of 2-mercapto-3-phenylquinazolin-4(3H)-one with ethyl chloroacetate. The quinazoline ring forms a dihedral angle of 86.83 (5)° with the phenyl ring. The terminal methyl group is disordered by a rotation of about 60° in a 0.531 (13): 0.469 (13) ratio. In the crystal, C—H...O hydrogen-bonding interactions result in the formation of columns running in the [010] direction. Two parallel columns further interact by C—H...O hydrogen bonds. The most important contributions to the surface contacts are from H...H (48.4%), C...H/H...C (21.5%) and O...H/H...O (18.7%) interactions, as concluded from a Hirshfeld analysis.