The interference of the time‐invariant magnetic‐dipole contribution with the time‐noninvariant electric‐dipole contribution to the second harmonic (SH) provides a mechanism which is sensitive to the reduction of symmetry of Cr2O3 by antiferromagnetic ordering of spins. A pronounced polarization dependence of the SH on the sign of the order parameter is observed in the 1.7–3.1 eV spectral range. The effect is used to study the domain structure of Cr2O3 by use of a CCD camera. Exposure times in the order of minutes are sufficient to yield a high‐resolution image of domains in samples of 10 mm2.