Irritable bowel syndrome (IBS) is a functional gastrointestinal disorder characterized by abdominal pain, altered motility, and visceral hypersensitivity. Emerging evidence implicates G protein-coupled receptors (GPCRs) as key integrators of microbial, immune, endocrine, and neural signals in IBS pathophysiology. This review summarizes recent advances in understanding how GPCRs mediate gut immune regulation, microbiota–host crosstalk, metabolic signaling, and pain processing in IBS. Recent studies show that microbial metabolites (e.g., short-chain fatty acids, biogenic amines, and lipid mediators) signal through GPCRs on immune cells, epithelia, and neurons to influence intestinal homeostasis. On immune cells and neurons, GPCRs also mediate signals from external substances (such as fats, sugars, histamine, etc.) to regulate immune and neural functions. And there are challenges and future directions in targeting GPCRs for IBS, including patient heterogeneity and the complexity of host–microbiome interactions. This review provides a mechanistic framework for GPCR-based therapies in IBS.