4,5-Dichlorophthalimide (5,6-dichloro-1H-isoindole-1,3(2H)-dione) is a phthalimide derivative. It has been synthesized from 5,6-dichloro-1,3-isobenzofurandione and characterized by 1H ,13C-NMR and IR. The dipole moment, polarizability and first-order hyperpolarizability of 4,5-dichlorophthalimide have been investigated using ab initio and density functional theory calculations.