Ce-doped zirconolite–sphene samples [CaZr 1− x Ce x Ti 2 O 7 –(1−x) Ca 1−2 y Ce y TiSiO 5 ] 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 2M-zirconolite and sphene with x=0.3 and y=0.05–0.20. The limits of Ce 4+ 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.