The asymmetric unit of the triclinic polymorph of the title compound, C21H25N3O3, consists of two mol-ecules, whereas for the monoclinic polymorph Z' = 1 [Fun et al. (2009 ▶). Acta Cryst. E65, o445]. The two mol-ecules exhibit an E configuration with respect to the C=N bond. The mol-ecules are linked into dimers by N-H⋯O and C-H⋯O hydrogen bonds forming R 2 (2)(8) ring motifs. In addition, π-π inter-actions occur between nitro-phenyl groups [minimum centroid-centroid distance 3.940 (2) Å], stacking the molecules along the ac plane.