1,6-Diisocyanatohexane and dimethyl sulfoxide were exploited as crosslinking agent and reaction solvent, respectively, for gelatin modification. Crosslinked samples were fractionated and analyzed by thermogravimetric analysis, infrared spectroscopy, acid and base titrations, and swelling measurements. The yield of crosslinking was found to increase with increasing diisocyanate and gelatin concentrations and the amount of bound crosslinker was evaluated. The chemical analysis of the reaction products allowed the process parameters to be related to the properties of the textile/gelatin composites. For this purpose poly(propylene)-, poly(ethylene terephthalate)-, and cotton-based textiles were treated to prepare soft and dimensionally stable supported materials with a gel phase composed of gelatin.