This work represents a spectroscopic vibrational study of metal complexes having amino acids as ligands. Here, were analyzed ternary complexes having Zn(II), Cd(II) and Ni(II) as central metallic ions with the following amino acids: cysteine, methionine, aspartic acid, serine, and with guanido acetic acid. The study was extended to one binary complex of Ni(II) with the guanidoacetic acid acting as ligand. The rigorous vibrational analyses allied to the complexes characterizations and to the theoretical calculations, were the fundamental and precious recourses in this research work. The infrared and/or vibrational spectroscopic information of metal – amino acids complexes are incomplete related to the vibrational characterization of all the normal modes, also we find lack of information referred to characterization and structural analysis. Allied to this fact, the lack of information or references in scientific literature on vibrational spectra of metal complex having amino acids as ligands, had a great contribution to elect the subject of this research. For the complexes characterization were used the following techniques: infrared analysis, thermo gravimetric analysis, elementary analysis and Raman spectroscopy. The quantum mechanical procedures were basically substantiated on the Density Functional Theory (DFT) with the B3LYP method and with the basis set 6-311G (d, p). The Natural Bond Orbital (NBO) was also determinate for two Ni(II) complexes. The intention here was to know the real hybridization of the metallic cation in the complex formation as well as the hybridization of the atoms which are inside of the coordination sphere of the central metallic ion. Joint to the utilization of these research sources, concerning the vibrational spectra, we carried out the second derivative interpretation for the infrared and Raman spectra, and using this information we extended the interpretation study of the normal modes to the deconvolution band analysis. This technique allowed us to put in evidence the overlapped bands, in such a way we are able to obtain almost all the fundamental bands in the vibrational spectrum. The research work present also a new way to assign the normal modes based on the characterization of the distorted geometry of the different normal modes, concluding with the theoretical and experimental assignment of the different vibrational spectra of these complexes. The conclusions point out to the consideration of the great importance which has the correct interpretation or assignment of the fundamental bands in the vibrational spectra of bioinorganic coordination compounds, essentially with the purpose to elucidate the low energy region where the metal – ligand vibrational modes are localized. The procedure of the integrated methodologies used here result in a precise and well substantiated vibrational analysis.