Organic–inorganic materials in which the organic part is constituted of dendrimers possessing one phosphorus atom at each branching point are reviewed. These dendrimers are either inside the materials and contribute to their elaboration, or they are linked to the surface of inorganic materials by covalent or electrostatic interactions. In the first case, the dendrimers have been used to organize and “glue” the inorganic elements or to generate nanoporosities after removal of the dendrimers used as templates. The non-covalent approach for controlled modifications of inorganic surfaces allows the synthesis of nanotubes made of 20 bilayers of oppositely charged dendrimers deposited on porous alumina templates. The covalent approach allowed the elaboration of stable, reusable, and highly sensitive DNA chips as well as piezoelectric membranes usable as biosensors.