We review the synthesis, properties and applications of spin crossover polymer composites, polymers and some related ‘soft’ materials. These materials have received recently much attention because they provide an efficient way for the processing of spin crossover complexes in various shapes at various size scales and can give rise also to unique physical properties. First, we discuss in detail the state of the art of the elaboration of spin crossover polymer composites, using either inorganic complex precursors in solution or preformed spin crossover powder. A particular attention is paid on the influence of the polymer matrix on the spin crossover properties and on the use of ‘active’ polymers for development of synergies between the properties of the matrix and the load. Polymer composite devices for applications in the fields of artificial muscles, energy harvesting and thermochromic sensors are also highlighted. Then, more recent works, in which organic polymeric chains are used as ligands for the transition metal ions are presented. Finally, we overview various related ‘soft’ spin crossover compounds including spin crossover dendrimers, gels, liquid crystals and Langmuir Blodgett films with particular emphasis on compounds with supramolecular interactions of alkyl chains.