Ce-doped zirconolite–sphene samples [CaZr1−xCexTi2O7–(1−x) Ca1−2yCeyTiSiO5] were prepared by the conventional solid-state reaction method using natural zircon. The samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) in order to determine the limit of Ce incorporation in Synroc mixture and their microstructures. The main crystalline phases were found to be 2 M-zirconolite and sphene with x = 0.3 and y = 0.05–0.20. The limits of Ce4+ ion incorporation in the zirconolite–sphene were determined to be x = 0.3 and y = 0.2. Powder XRD and differential scanning calorimetry (DSC) investigations suggest that the solid reaction scheme is complex and the Ce-doped zirconolite–sphene Synroc was probably initially formed at 1060 °C.