The high-resolution far-infrared absorption spectrum of the gaseous molecular complex H3N-HCN is recorded by means of static gas-phase Fourier transform far-infrared spectroscopy at 247 K, using a synchrotron radiation source. The spectrum contains distinct rotational structures which are assigned to the intermolecular NH3 libration band v(9)(1) (v(B)) of the pyramidal H3N-HCN complex. A rovibrational analysis based on a standard semirigid symmetric top molecule model yields the band origin of 260.03(10) cm(-1), together with values for the upper state rotational constant B' and the upper state quartic centrifugal distortion constants D'(J) and D'(JK). The values for the upper state spectroscopic constants indicate that the hydrogen bond in the H3N-HCN complex is destabilized by 5% and elongates by 0.010 angstrom upon excitation of a quantum of libration of the hydrogen bond acceptor molecule.