Quorum sensing is a cell-to-cell communication process in bacteria, where the production and detection of extracellular chemicals called autoinducers enable bacteria to monitor cell population density and synchronize gene expression. This review focuses on the quorum-sensing systems of *Vibrio harveyi* and *Vibrio cholerae*, highlighting their differences and similarities with other bacterial signal transduction systems. The *Vibrio* quorum-sensing systems are optimized to translate extracellular autoinducer information into internal changes in gene expression. Studies of these systems have revealed fundamental mechanisms underlying collective behaviors, such as small-molecule biosynthesis, signal detection and transduction, information processing, and post-transcriptional control of mRNA levels. The LuxIR-type quorum-sensing systems in Gram-negative bacteria use acyl homoserine lactones (AHLs) as autoinducers, while Gram-positive bacteria use modified oligopeptides. The two-component quorum-sensing systems in Gram-positive bacteria involve membrane-bound histidine kinase receptors and cytoplasmic response regulators. The quorum-sensing network architecture in *V. harveyi* and *V. cholerae* differs from the common LuxIR theme, with unique components and mechanisms. The autoinducers HAI-1, AI-2, and CAI-1 are synthesized by cytoplasmic enzymes and detected by membrane-bound histidine kinases. The signal transduction pathway involves phosphorylation and dephosphorylation cascades, with multiple two-component proteins involved. The Qrr sRNAs play a crucial role in controlling gene expression by regulating the production of the master regulator LuxR/HapR. In *V. harveyi*, the Qrr sRNAs function additively, while in *V. cholerae*, they function redundantly. The information from multiple autoinducers is processed through shared phosphorelay cascades, allowing bacteria to distinguish between different signals.Quorum sensing is a cell-to-cell communication process in bacteria, where the production and detection of extracellular chemicals called autoinducers enable bacteria to monitor cell population density and synchronize gene expression. This review focuses on the quorum-sensing systems of *Vibrio harveyi* and *Vibrio cholerae*, highlighting their differences and similarities with other bacterial signal transduction systems. The *Vibrio* quorum-sensing systems are optimized to translate extracellular autoinducer information into internal changes in gene expression. Studies of these systems have revealed fundamental mechanisms underlying collective behaviors, such as small-molecule biosynthesis, signal detection and transduction, information processing, and post-transcriptional control of mRNA levels. The LuxIR-type quorum-sensing systems in Gram-negative bacteria use acyl homoserine lactones (AHLs) as autoinducers, while Gram-positive bacteria use modified oligopeptides. The two-component quorum-sensing systems in Gram-positive bacteria involve membrane-bound histidine kinase receptors and cytoplasmic response regulators. The quorum-sensing network architecture in *V. harveyi* and *V. cholerae* differs from the common LuxIR theme, with unique components and mechanisms. The autoinducers HAI-1, AI-2, and CAI-1 are synthesized by cytoplasmic enzymes and detected by membrane-bound histidine kinases. The signal transduction pathway involves phosphorylation and dephosphorylation cascades, with multiple two-component proteins involved. The Qrr sRNAs play a crucial role in controlling gene expression by regulating the production of the master regulator LuxR/HapR. In *V. harveyi*, the Qrr sRNAs function additively, while in *V. cholerae*, they function redundantly. The information from multiple autoinducers is processed through shared phosphorelay cascades, allowing bacteria to distinguish between different signals.