This work was aimed to study the effect of natural polyphenols extract (Acacia nilotica bark) on physicochemical properties of crosslinked gelatin-poly(acrylamide-co-acrylic acid), Gel-poly(AAm-co-Ac), polymeric biocomposite film. Gelatin-based composite films have extensive application as biocompatible biomaterial as drug carriers, cosmetics, and agricultural food packaging. The prepared composite films were characterized using Fourier transform infrared spectroscopy (FTIR) and differential scanning calorimetry (DSC), in addition to the swelling and degradation behavior. UV-Vis absorption spectra and scanning electron microscopy (SEM) were also applied to observe the interaction between Gel-poly(AAm-co-Ac) and natural polyphenol (catechin). The study has demonstrated that the involvement of hydrogen bonding and hydrophobic interactions as the major forces involved in the stabilization of gelatin-based polymeric biocomposite film by the plant polyphenols (catechin and gallic acid derivatives). Thermal stability studies of crosslinked gelatin-based composite film revealed that A. nilotica bark extract stabilizes the gelatin molecules and leads to moderate increase of the denaturation temperatures relative to the uncrosslinked one. (C) 2010 Wiley Periodicals, Inc. J Appl Polym Sci 116: 2825-2832, 2010