This paper presents a structural and vibrational study of a new compound, namely, monohydrate 1,5-pentanediammonium hydrogen sulfate (NH3(CH2)5NH3(HSO4)2.H2O). The X-ray crystal structure shows that this compound crystallizes in the monoclinic system, space group P2(1)/c, with the lattice parameters a=9.2250(2)A, b=7.7540(4)A, c=20.8520(1)A, beta=116.23(3) degrees, V=1337.97(10)A3, and Z=4. From the structural investigations, it is found that the studied compound is built by infinite anionic ribbons parallel to the "a" axis. These ribbons form tunnels in which organic cations are inserted. Infrared (IR) spectrum of the compound in the 300-4000 cm(-1) spectral region is reported. A tentative assignment of the observed bands, supported by a molecular orbital semi-empirical calculation, is given.