Quercetin is a plant-derived flavonoid found in various fruits, vegetables, and beverages, and it is known for its potent antioxidant, anti-inflammatory, and immune-modulating properties. Its role in managing chronic diseases has been widely studied, showing promise in several areas. Quercetin and quercetin-rich foods have been reported to have a wide range of health-promoting effects, especially in the prevention and management of several diseases; however, its solubility and bioavailability have limited its use. It is beneficial in diseases with an inflammatory component, such as rheumatoid arthritis, inflammatory bowel disease (IBD), and asthma, inhibiting the inflammatory pathways by suppressing pro-inflammatory cytokines (e.g., TNF-α, IL-6) and enzymes (e.g., COX-2). It prevents or reduces oxidative stress-linked conditions like cardiovascular diseases (CVDs), neurodegenerative disorders (e.g., Alzheimer's), and diabetes, as Quercetin neutralizes free radicals and upregulates antioxidant defenses (e.g., glutathione). It has a potential role in managing hypertension, atherosclerosis, and heart disease as it improves endothelial function, reduces blood pressure, and lowers LDL cholesterol by enhancing nitric oxide bioavailability and reducing lipid peroxidation. It is a proven fact that the consumption of Quercetin improves insulin sensitivity, lowers blood glucose levels, reduces complications by modulating glucose transporters, inhibits α-glucosidase enzymes, and protects pancreatic β-cells from oxidative damage. Due to its multifunctional biological effects, Quercetin holds significant potential in managing chronic diseases. While it is not a substitute for standard medical treatments, it can be an effective complementary approach under professional guidance. This review explores the current literature surrounding quercetin’s versatile properties, mechanisms of action, and its role in the prevention and treatment of conditions such as cardiovascular diseases, diabetes, cancer, and other diseases.