In the title compound, C10H8ClN3O2, the indazole ring system makes a dihedral angle of 7.9 (3)° with the plane through the nitro group. The allyl group is rotated out of the plane of the indazole ring system [N-N-C-C torsion angle = 104.28 (19)°]. In the crystal, mol-ecules are linked by C-H⋯O hydrogen bonds, forming zigzag chains propagating along the b-axis direction.