This chapter presents the use of poly(phosphorhydra- zone) (PPH) dendrimers for the functionalization of solid surfaces, either by non-covalent or covalent interactions, and the use of some of the obtained devices as nano-tools for biology, particularly as biosensors. The main advantage of using dendrimers compared to monomers for the functionalization of solid surfaces is the large number of anchoring points, which should enhance the stability. Compared to polymers, dendrimers induce a high reproducibility, due to their precisely controlled structure. There are different ways to functionalize surfaces by non-covalent interactions, depending on whether the functional entities are neutral or charged. A more specific interaction was obtained with a small PPH dendrimer having a pyrene emanating from the core and palladium complexes of phosphines as terminal functions. The LbL process was carried out also using positively charged dendrimers and negatively charged gold nanoparticles.