An emerging group of hybrid materials is the so-called bio-nanocomposites, which are bio-hybrid nanostructured materials based on the combination of natural polymers (polysaccharides, proteins, enzymes, nucleic acids) and inorganic solids (clays, double layered hydroxides, phosphates, metal oxides, etc.). Bio-nanocomposites are interesting because, among other properties, the use of biopolymers provides biocompatibility, non-toxicity and biodegradability to the resulting nanohybrid materials. An example of this type of natural polymers is gelatin, a polypeptide derived from the structural protein collagen, that is able to form transparent, elastic and thermoreversible gels. This paper will review the role of inorganic solids, such as montmorillonite or perovskite, in combination with gelatin, on the characteristics and final properties of different type of bio-nanocomposites based on this protein. With these examples, we will show the influence of the solids on the gelatin gel-transition temperature, film formation ability and rheological, mechanical and dielectric properties.