Thermodynamic descriptions of binary Ca-Ce and ternary Mg-Ca-Ce systems were generated using the Calphad method. Complementary experimental study of phase equilibria and solidification microstructures was done using metallography, scanning electron microscope with energy dispersive X-ray microanalysis and differential scanning calorimetry. The microstructures of these Mg-rich alloys formed during slow solidification and the type and sequence of solid phase precipitation compares well with thermodynamic equilibrium and non-equilibrium calculations.