Terahertz (THz) absorption spectra of organogels consisting of (1R,2R)-1,2-bis(dodecanoylamino)cyclohexane/2-nitrophenyl octyl ether (RR-BDC/NPOE) and RR-BDC/n-dodecane were measured by Fourier-transform far-infrared (FT-FIR) spectroscopy. The vibrational peaks of the gels were observed at the same frequencies as those of the pure gelator, suggesting that the intermolecular structure around the NH⋯OC hydrogen bond is maintained in the gel phase. Temperature-dependent spectroscopy showed a drastic spectral change at the sol–gel transition temperature, in which the vibrational peak at 3.5THz disappears and a new peak appears at 2.9THz. The change in THz vibrational frequency is indicative of the structural collapse of the hydrogen-bonded fibrous architecture in the sol phase.