The molar heat capacity, C-p,C-m, of a complex of erbium chloride coordinated with L-proline, [Er(Pro)(2)(H2O)(5)]Cl-3, was measured from T) 80 K to T) 400 K with an automated adiabatic calorimeter. The temperature, the molar enthalpy, and the entropy of fusion and decomposition were calculated using equations and diagrammatic area integration. The thermodynamic functions [H-T-H-298.15] and [S-T-S-298.15] were derived from T = 80 K to T = 360 K with a temperature interval of 5 K. The thermal stability of the compound was investigated by differential scanning calorimetry and the thermogravimetric techniques.