Based on our earlier results on the theoretical and experimental study of potassium O,O-diethyldithiophosphate, the normal modes of nickel and zinc O,O-diethyldithiophoshate complexes were elucidated. Infrared and Raman spectra of these compounds were recorded. Quantum chemical calculations resulted in optimized structures, electric charge distributions, vibrational force constants, and fundamental frequencies. Normal coordinate analysis was applied to characterize the vibrational modes. Based on the results of these calculations vibrational spectra were simulated. The largest spectral differences between the two complexes appeared in vibrational modes encompassing the central part of the formula unit viz. PS2MS2P, where M is the metal atom. Namely, this central part of the Ni complex has D2h symmetry, while that of the Zn one has D2d symmetry.