Dendrimers are highly branched macromolecules, which have properties in many different fields, in particular for catalysis. This review presents an exhaustive view about complexes of phosphorus-containing dendrimers (having a phosphorus atom at each branching point), used as homogeneous catalysts in a range of reactions. First, catalysed reactions for C–C bonds formation using Pd, Rh, Ru, or Sc complexes will be displayed; then formation of C–O and C–N bonds using Cu complexes as catalysts will be shown. At the end, miscellaneous reactions catalysed without metal (organocatalysis) will be displayed. Despite their size, dendrimers are generally soluble in the reaction media, thus they afford homogeneous catalysts. However, their size is by far larger than the size of the reagents and products, thus they are generally easily separated, simply by adding a solvent in which the products are soluble, but not the dendrimers. The recovery and reuse of dendrimers (recycling) is an important advantage compared to classical monomeric catalysts, which will be emphasized in this review, together with the so-called dendrimer (or dendritic) effect, which is an enhancement of a property when the size of the dendrimer increases.