Corn protein (zein) was melt-processed with methylenediphenyl 4,4'-diisocyanate (MDI) using triethylamine (TEA) as a catalyst to facilitate the reaction of the isocyanate groups with the nucleophilic moieties present on zein. The product of the reaction was examined using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) to monitor changes in molecular weight. Techniques used to evaluate property changes after reaction included FTIR, differential scanning calorimetry (DSC), thermogravimetric analysis (TGA), and evaluation of mechanical properties. Our findings demonstrated that zein reacts with MDI in the melt state generating higher molecular weight compounds that after compression molding have improved physical properties and solvent resistance.