The equilibrium nuclear configuration and the potential energy and dipole moment component surfaces of an isolated Li+–CO complex are calculated quantum-mechanically in the MP4(SDQ)/6-311++G(3df) approximation. The geometrical parameters and the binding energy of the complex are determined. The frequencies and intensities for the fundamental transitions are calculated in the harmonic approximation. The one-, two-, and three-dimensional anharmonic vibrational Schrödinger equations are solved using the variational method. The energies of states of a three-dimensional vibrational system, anharmonic constants, and the frequencies and intensities of fundamental transitions are determined with the anharmonic interactions taken into account. The changes in the frequency and intensity of the C–O stretching vibration upon the formation of the complex are predicted.