Biofilm formation is closely related to bacterial infection and is also a mechanism of antimicrobial resistance. Hence, the antibiofilm approach provides an alternative to an antibiotic strategy. In this study, the antibiofilm activities of resveratrol (1) and five of its oligomers, namely, ε-viniferin (2), suffruticosol A (3), suffruticosol B (4), vitisin A (5), and vitisin B (6), were investigated against enterohemorrhagic Escherichia coli O157:H7 and Pseudomonas aeruginosa PA14. Vitisin B (6), a stilbenoid tetramer, was found to inhibit biofilm formation by the two bacteria the most effectively and at 5 μg/mL inhibited E. coli O157:H7 biofilm formation by more than 90%.