In the mol-ecule of the title compound, C7H9ClN2O2, the conformation is determined by intra-molecular C-H⋯O and C-H⋯Cl hydrogen bonds, which generate S(6) and S(5) ring motifs. The isopropyl group is almost perpendicular to the pyrimidine ring with torsion angles of -70.8 (3) and 56.0 (3)°. In the crystal, two inversion-related mol-ecules are linked via a pair of N-H⋯O hydrogen bonds into R 2 (2)(8) dimers; these dimers are connected into chains extending along the bc plane via an additional N-H⋯O hydrogen bond and weaker C-H⋯O hydrogen bonds. The crystal structure is further stabilized by a weak π-π inter-action [3.6465 (10) Å] between adjacent pyrimidine-dione rings arranged in a head-to-tail fashion, producing a three-dimensional network.