A comprehensive investigation of the ground state structural, spectral and electronic properties of Pyridine and Pentachloropyridine (PCP) have been performed using B3LYP/6-311++G (d,p) level of theory. The complete vibrational assignment and analysis of the fundamental modes of both molecules were carried out using theoretical and experimental FTIR spectral data. The effect of substitution of electronegative chlorine atoms at the Pyridine ring, on the structural, vibrational and other properties has been analyzed and discussed. The frontier molecular orbitals analysis and molecular electrostatic potential surface (MESP) map have also been calculated to get a better insight of the properties of the title molecules. The mean polarizability of PCP is found to be 3.66 times more than Pyridine, whereas the dipole moment for Pyridine and PCP are calculated to be 2.3654 and 1.5262 Debye respectively.