Although the preparation of CeSiO₄ has been already reported, the formation of pure cerium silicate from aqueous precursors appears as a challenge. An innovative way of synthesis has been identified in this study, allowing the formation of CeSiO₄ after hydrothermal treatment starting from Ce(III) silicate precursors. Among the experimental parameters examined, significant effects were found according to the nature of the precursor and of the reactive media considered, the pH of the reactive media and the temperature of the hydrothermal process. This study allows the determination of optimized conditions for the hydrothermal synthesis of pure CeSiO₄ (A-Ce₂Si₂O₇ or Ce_4.67(SiO₄)₃O as starting precursors, nitric medium, pH = 7, 7 days at 150 °C). The in situ low oxidation rate of Ce(III) into Ce(IV) was a key parameter to consider in order to avoid the presence of CeO₂ in the final mixtures.