In the title compound, C(16)H(17)ClN(4)O(2), the aromatic ring is twisted slightly with respect to the plane of the diazene group [N-N-C-C torsion angle = -3.9 (4)°]. The NO(2) group is twisted by 16.2 (4)° relative to the aromatic ring. The two ethyl chains are positioned such that one ethyl chain lies above and the other below the ring.