The viscosity of 16 compositions of potassium chloraluminate systems containing 3.8–57.2 mol % of ZrCl4 and 5.4– 30.2 mol % of HfCl4 was determined in the temperature range of 563–663 К. Their temperature dependences are given. Binary chloraluminate mixtures containing HfCl4 additions were found to have the highest viscosity, and those containing ZrCl4 ones had the lowest viscosity. The viscosity of the three-component system has an intermediate value. The obtained results can be used in the technology of separation of zirconium and hafnium tetrachlorides.