Dietary fiber (DF) is that part of plant material in the diet which is resistant to enzymatic digestion and includes cellulose, polysaccharides such as hemicellulose, pectin substances, gums, mucilage and a non-carbohydrate component lignin. DF is often divided into two parts when it is dispersed in water: a soluble and an insoluble fraction, each fraction has different physiological effects. High-fiber diets are associated with the prevention and treatment of some diseases such as constipation, diverticular disease, colonic cancer, coronary heart disease and diabetes. Daily intake for total fiber for adults has been set at 38 g for men and 25 g for women. DF is obtained by different methods and from different sources. The amount and composition of fiber differ from one food to another. DF from cereal bran is a typical ingredient in high DF food products, but the presence of soluble DF in cereals is quite low, this is not the case with fruits where the ratio between soluble and insoluble DF fractions is more balanced. Influence of different processing treatments (like extrusion-cooking, canning, grinding, boiling, frying) alters the physico-chemical properties of dietary fiber and improves their functionality. Dietary fiber can provide a multitude of functional properties when they are incorporated in food systems. Thus, fiber addition contributes to the modification and improvement of texture, sensory characteristics and shelf-life of foods due to their water binding capacity, gel-forming ability, fat mimetic, antisticking, anticlumping, texture rising and thickening effects. Dietary fiber can be used in various functional foods like bakeries, drinks, beverages and meat products. Dietary fiber can be determined by different methods, mainly by enzymatic gravimetric and enzymatic chemical methods.