The thermal decomposition of tris(ethylenediamine)cobalt(III) complexes was investigated through the use of thermogravimetry, derivative thermogravimetry, differential thermal analysis, thermomagnetic analysis, infrared spectroscopy, reflectance spectroscopy, mass spectroscopy, and evolved gas analysis. Data were collected, compiled, and analyzed in order to determine the thermal decomposition mechanism for the complexes. Intermediates were identified for the chloride, bromide, iodide, thiocyanate, nitrate and bisulfate complexes. Some of the thermal data were explained in terms of the kinetics of the mechanism steps.