Raman spectra of p-nitroaniline in supercritical water and supercritical alcohols were measured, and the effects of solvents on the NO2 and NH2 stretching modes were investigated. The intensity and frequency of the NO2 stretching mode significantly changed as a function of the solvent density and temperature. The frequency of the NO2 stretching mode correlated with the absorption peak energy of the SI-So transition. On the other hand, the vibrational frequency of the NH2 stretching mode did not correlate with the absorption peak shift, although it had a large frequency shift as a function of the density. The correlation between the NO2 frequency and absorption peak energy suggested that the solvent effects of supercritical water and supercritical alcohols were similar to those for nonpolar solvents. The density functional calculation using the polarizable continuum model and p-nitroaniline- water clusters qualitatively reproduced the density dependence of the NO2 stretching mode as well as the solvent polarity dependence. Detailed vibrational analysis revealed that the coupling between the NO2 and C-NH2 vibrational motions at the harmonic level has an important effect on the intensity and frequency shift of the NO2 stretching mode. The frequency shift of the NH2 stretching mode correlated with the degree of hydrogen bonding between the solvent molecules estimated from NMR measurements [Hoffmann M. M.; Conradi, M. S. J. Phys. Chem. B. 1998, 102, 263]. The existence of intermolecular hydrogen bonding around the NH2 group was demonstrated even at low-density conditions.