tCarrageenan-based antimicrobial films were developed by incorporation of grape fruit seed extract (GSE)at different concentration into the polymer using a solvent casing method and their physical, mechanical,and antimicrobial properties were examined. The carrageenan/GSE composite films appeared yellowishtint due to the polyphenolic compounds in the GSE. SEM analysis showed rough surface with sponge likestructures on the cross section of the films. FT-IR results indicated at GSE had good compatibility withcarrageenan. The amorphous structure of polymer films was not changed by the incorporation of GSE.But, the addition of GSE increased moisture content, water vapor permeability, and surface hydrophilicityof the films. The tensile strength and elastic modulus decreased with increasing content of GSE, how-ever, the elongation at break increased significantly up to 6.6 g/mL of GSE then decreased thereafter.Thermal stability of the films was not influenced by GSE incorporation. The carrageenan/GSE compositefilms exhibited great antibacterial activity against food borne pathogens. These results suggest that thecarrageenan-based composite films have a high potential for being used as an antimicrobial or activefood packaging applications.