Metal oxide/polymer hybrids are prepared from polystyrene nanoparticles functionalized at the surface with phosphonate and phosphate groups. The polymer particles are synthesized with specifically designed surface-active monomers (surfmers) and used as nucleation surfaces for the controlled in situ crystallization of cerium, iron, and zinc oxide nanocrystals. The formation of the metal oxide is driven by the addition of a base to suspensions of the polymer particles containing the corresponding precursor. The crystal formation at the particle surface is studied for the different hybrid systems by X-ray diffraction and transmission electron microscopy (TEM). The potential catalytic activity of CeO2/polymer hybrid particles is proven with the example of the photodegradation of rhodamine B. For the case of magnetic iron oxide-functionalized latex, a superparamagnetic behavior is found above a blocking temperature of 225 K. ZnO/polymer hybrids present a strong yellow visible photoluminescence. The approach is shown to be versatile not only in terms of the variety in the metal oxides deposited on the surface, but also because the crystallization can take place in both aqueous and alcoholic media.