2,4,6-Trichloronitrobenzene (TCNB) was examined by means of ^<35>Cl NQR, and two modifications (α- and β-forms) were found. In the enform two resonance lines were observed at room temperature and 77 K, and in the β-form two resonance lines were also found. The lower frequency and the higher frequency lines in each of the modifications were assigned to the chlorine atoms at the para- and ortho-positions, respectively. Zeeman study of ^<35>Cl NQR lines was carried out at room temperature in a single crystal of β-TCNB. It was revealed that the crystal of β-TCNB belongs to a tetragonal system with D_<2d> or D_<4h> symmetry. The angles between the C-Cl bonds and the angles between the plane of the benzene ring and the crystal planes were determined on the basis of the directions of the principal efg axes. The values of the quadrupole coupling constants and the asymmetry parameters were determined. The bond characters of the C-Cl bonds were calculated from the NQR parameters.