Propyl gallate (PG), a phenolic antioxidant widely used in the food industry, has recently been noted for its potential antimicrobial and antivirulence activities. However, its effects on major aqua- culture pathogens remain insufficiently characterized. In this study, we comprehensively evaluated the antibacterial, antibiofilm, and quorum-sensing (QS)-related inhibitory effects of PG against Edwardsiella tarda (E. tarda) and Vibrio anguillarum (V. anguillarum). PG exhibited strong anti- microbial activity, showing MIC values of 7.8 μg/mL for both species, and growth curve and time-kill assays confirmed concentration-dependent growth suppression and complete killing at higher concen- trations. At sub-MIC levels, PG significantly reduced biofilm formation and impaired both swimming and swarming motilities. Violacein-based assays using Chromobacterium violaceum (C. violaceum) further demonstrated that PG inhibited QS-regulated pigment production without affecting bacterial viability. qPCR analysis showed reduced expression of key QS-associated genes, including luxR, luxS, and QseB in E. tarda and vanO in V. anguillarum. Collectively, these transcriptional changes, together with alterations in QS-regulated phenotypes, suggest that PG may partially interfere with AHL- and AI-2-mediated QS signaling pathways. Overall, our findings indicate that PG possesses both bacter- icidal and antivirulence properties and highlight its potential as a safe and eco-friendly alternative or adjunctive agent for disease management in aquaculture.