The triazole compound 4-(3-(1H-imidazol-1-yl)propyl)-5-methyl-2H-1,2,4-triazol-3(4H)-one monohydrate has been synthesised and characterised by H-1-NMR, C-13-NMR, IR, and X-ray single-crystal determination. The compound crystallizes in the triclinic space group P (1) over bar with a = 9.0366(7) angstrom, b = 11.5690(8) angstrom, c = 12.0571(9) angstrom, alpha = 110.733(6)degrees, beta = 94.172(6)degrees, gamma = 98.085(6)degrees and Z = 4. In addition to the molecular geometry from X-ray determination, the molecular geometry, vibrational frequencies and gauge, including atomic orbital (GIAO) H-1-and C-13-NMR chemical shift values of the title compound in the ground state, were calculated using the density functional method (B3LYP) with the 6-31G(d) basis set. The calculated results show that the optimised geometries can well reproduce the crystal structure, and the theoretical vibrational frequencies and chemical shift values show good agreement with experimental values. The energetic behaviour of the title compound in solvent media was examined using the B3LYP method with the 6-31G(d) basis set by applying the Onsager model. The total energy of the title compound decreases with increasing polarity of the solvent. The predicted nonlinear optical properties of the title compound are greater than those of urea. In addition, DFT calculations of the molecular electrostatic potentials, frontier molecular orbitals and thermodynamic properties of the title compound were carried out at the B3LYP/6-31G(d) level of theory.