Raman and FTIR spectra of nicotinic acid have been analysed using ab-initio and DFT calculations. Four stable structures were found for nicotinic acid, the structures differ in orientation of COOH with respect to the nitrogen atom. The optimized geometries, harmonic vibrational wave number, structural parameters and intensities of the nicotinic acid have been calculated using MP2/6-311++G(d,p), B3LYP/6-311++G(d,p), B3PW91/6-311++G(d,p), X3LYP/6-311++G(d,p) level of theories. Vibrational assignments have been made and calculated DFT frequencies and Raman intensities of nicotinic acid are found to be in better agreement with corresponding experimental values in comparison to previous results. Selected experimental bands were assigned based on scaled theoretical wave numbers.