In the title compound, C18H15Cl2N3O2Se, the selenadiazole ring makes dihedral angles of 49.87 (3) and 55.70 (3)° with the two benzene rings. The dihedral angle between the two benzene rings is 11.90 (5)°. In the crystal structure, intramolecular C—H⋯O and C—H⋯Se interactions and intermolecular C—H⋯O, C—H⋯Cl and C—H⋯N interactions are observed