The design and engineering of innovative bionanocomposites for a wide variety of applications should be based on the understanding of the relationship between their nanoscale structure and their chemical and mechanical properties. The understanding of the chemistry and structure at the nanometric level imply an essential knowledge for future developments of novel materials based on polysaccharides and nanostructured materials toward several applications (for instance bioremediation, medical applications, biotechnology, food industry, etc.). The study of the physicochemical characteristics of a material would imply not only its basic description but could be significantly relevant in the optimization of its synthesis toward the obtaining of tailored properties or the control of the material behavior in a particular application. Herein, we present the introduction to the most used techniques in the characterization of bionanocomposites, such as electron microscopies, FTIR, Raman spectroscopy, NMR, Rheology behavior, DSC, TGA, SAXS and SANS. The basics of these techniques and key approaches in the characterization of bionanocomposites are presented for the understanding of the relevance of the characterization step in a material evaluation.