Gut microbiota plays a critical role in maintaining human health by regulating digestion, metabolism, and immune function. Emerging research highlights the potential of dietary interventions, particularly dietary fiber (DF) and polyphenols, in modulating gut microbiota composition and function. DF serves as a fermentable substrate for beneficial gut bacteria, promoting the production of short-chain fatty acids (SCFAs). Polyphenols, a diverse group of bioactive compounds selectively modulate microbial populations and contribute to the production of bioactive metabolites with host health benefits. Importantly, the interplay between DF and polyphenols creates a synergistic effect within the gut microbiome, shaping microbial diversity, enhancing SCFAs production, and strengthening gut barrier function, which together support metabolic and immune homeostasis. This review systematically explores the synergistic effects of DF-polyphenol combinations on gut microbiota modulation, microbial metabolites, and their implications for overall health. The combined effects of DF and polyphenols hold promise for targeted nutritional strategies in preventing metabolic disorders and improving gut health. Moreover, the extent of these benefits is influenced by the structural characteristics of DF, the source and dosage of polyphenols, and individual gut microbiota composition. Further research is warranted to optimize DF-polyphenol interactions and facilitate their applications in personalized nutrition and functional food development.