Chitosan interacts with proanthocyanidins through hydrogen-bonding, which allows encapsulation and development of stable nanoparticles via ionotropic gelation. Cranberry proanthocyanidins (PAC) are associated with the prevention of urinary tract infections and PAC inhibit invasion of gut epithelial cells by extra-intestinal pathogenic Escherichia coli (ExPEC). We determined the effect of cranberry proanthocyanidin-chitosan hybrid nanoparticles (PAC-CHTNp) on the ExPEC invasion of gut epithelial cells in vitro. PAC-CHTNp were characterized according to size, morphology, and bioactivity. Results showed a decrease in the size of the nanoparticles as the concentration of PAC was increased, indicating that PAC increases cross-linking by hydrogen-bonding on the surface of the chitosan nanoparticles. Nanoparticles were produced with diameters ranging from 367.3nm to 293.2nm. Additionally, PAC-CHTNp significantly inhibited the ability of ExPEC to invade the enterocytes by ~80% at 66mugGAE/mL and by ~92% at 100mugGAE/mL. Results also indicate that chitosan nanoparticles alone were not significantly different from controls in preventing ExPEC invasion of enterocytes (data not shown) and also there were not significant differences between PAC alone and PAC-CHTNp, suggesting that the new PAC-CHTNp could lead to an increase in the stability of encapsulated PAC, maintain the molecular adhesion of PAC to ExPEC.