The thermal properties of some mixed complexes of cobalt(III) containing tetradentate ethylenediamine-N,N'-di-3-propionate (eddp) ligand and several amino acids were investigated by thermogravimetry (TG) and differential scanning calorimetry (DSC). The thermal stability derived from decomposition temperatures was discussed in terms of amino acid present. It was shown that the processes of thermal decomposition of these complexes are multi-step degradation processes. Some of these can be separated into individual steps. The corresponding kinetic and thermodynamic parameters of these processes were determined, and the possible mechanisms were discussed.