Dietary fibers primarily consist of carbohydrates and are derived from plant-based sources. Two distinct categories exist depending on their solubility in water, namely soluble and insoluble dietary fibers. These substances are indigestible and/or absorbable by the human body. They play a crucial function in the maintenance of optimal health. Recent research indicates that high-fiber diets, particularly those containing soluble dietary fibers, can effectively manage weight and protect against obesity, ulcerative colitis, diabetes, cardiovascular diseases, hypertension, gastrointestinal diseases, diverticulosis, hemorrhoids, and colon cancer. Although subject to ongoing debate, a proposition suggests that fiber may have potential benefits for those diagnosed with diabetes mellitus, namely in managing their blood glucose levels following a meal and enhancing carbohydrate metabolism. This chapter explores the functional aspects of dietary fiber in nutraceuticals, emphasizing its role in promoting human health and well-being. The chapter covers the various types of dietary fiber, their sources, and their potential applications in formulating functional food products. The chapter also delves into the physiological effects of dietary fiber consumption, its impact on gut microbiota, its potential role in preventing chronic diseases, and the harmful effects of consuming excessive dietary fiber.