Colloidal calcium phytate was prepared by anion-exchange of phosphate by phytate, starting from calcium phosphate nanoparticles. Scanning electron microscopy (SEM) showed spherical nanoparticles of narrow size distribution, in good agreement with dynamic light scattering (DLS) results, whose diameter could be adjusted between about 40 to 250 nm depending on the employed synthesis conditions. The particle surface is covered by phytate anions as indicated by the strongly negative zeta potential of −40 to −50 mV. The preparation of a stable colloid was only possible within a narrow range of the ratio of calcium to phytate. Infrared spectroscopy, X-ray diffraction and elemental analysis showed that the particles consisted of X-ray amorphous calcium phytate. The colloidal dispersions were stable for about two weeks before precipitation occurred.