The third-order nonlinear optical properties of the N-6-hydroxy-hexyl-4-azophenyl-carbazol have been investigated both theoretically and experimentally. Using Z-scan method with a femtosecond laser (440[Formula: see text]nm, 190[Formula: see text]fs), the third-order nonlinear optical properties of the N-6-hydroxy-hexyl-4-azophenyl-carbazol were determined. The second-order hyperpolarizability [Formula: see text] of the experiment result was found to be [Formula: see text][Formula: see text]esu. We have also calculated the second-order hyperpolarizability based on the sum-over-states (SOS) method. The theoretical value was in accord with the experiment result. The result showed that the N-6-hydroxy-hexyl-4-azophenyl-carbazol was one of the promising third-order nonlinear optical materials.