The aqueous solutions of Nicotinamide (NIA, vitamin B3), with various concentrations, are investigated at different temperatures applying Time Domain Reflectometry (TDR) technique. The complex dielectric spectra of NIA-water solutions are fitted with the Debye relaxation model and the dielectric relaxation parameters like static dielectric constant, relaxation time have been determined by non-linear least square fit method. The Excess dielectric parameters and Kirkwood correlation factors show a significant change in dipole orientation also indicates the formation of cluster structures within the mixture. The thermodynamic parameters, Arrhenius characteristics and viscosity effects are reported. The FTIR spectroscopy confirms the heteromolecular hydrogen bond formation, through functional group interaction in the mixture systems; moreover, the NIA-Water clusters are optimized and the hydrogen bond interactions are discussed. The resulting theoretical vibrational frequency of C = O and C-N bond of NIA is found to be consistent with experimental frequencies. © 2020 Informa UK Limited, trading as Taylor & Francis Group.