The heat capacity of K2ZnCl4 has been measured between 10 and 300 K using an adiabatic calorimeter. The low temperature phase transition is strongly influenced by the small amount of water remaining in the crystals which were grown from an aqueous solution. A sharp heat capacity anomaly is observed at 146.24 K for the sample dried under vacuum above 100-degrees-C for 30 h, and the enthalpy and entropy of transition are 57.16 J mol-1 and 0.387 J K-1 mol-1, respectively.