The absolute signs and magnitudes of the second‐order nonlinear optical coefficients,d14, of CuCl, CuBr, and CuI have been determined with laser fundamentals at 1.32, 1.06, and 0.95 &mgr;m. All threed14's are real, negative, and show no dispersion over the measured spectral range. Except for CuI, the magnitudes ofd14are in agreement with data at 1.06 &mgr;m reported earlier by Chemlaet al.The negative signs and magnitudes ofd14most likely require important Cu 3delectron contributions for their explanation.