In the title compound, C8H5ClN2Se, the dihedral angle between the planes of the selenadiazole and chlorophenyl rings is 16.6 (2)°. In the crystal, the packing of the molecules is consolidated by weak C—H...N hydrogen bonds, which generate [001] chains, and π–π stacking interactions are observed between the phenyl and selenadiazole rings, with a centroid–centroid distance of 3.884 (2) Å. There is also a short Se...Cl contact of 3.468 (1) Å