The objective of this work was to perform the ethanolic pretreatment of stevia leaves from the plant Stevia UEM-13 line and to characterize its physical-chemical properties aiming its use as a sweetener in the development of a diet cereal bar. The same formulation of the cereal bar with stevia leaves without pretreatment was elaborated for comparative purposes. The following ingredients were used in the preparation of the produtc: fine oat flakes, no sugar granola, cranberry, dehydrated apricots, water, gum acacia and stevia leaf pretreated (F1) and without treatment (F2). According to the results, the diet cereal bars presented significant amounts ​​of crude fiber, protein and antioxidant activity. The product was microbiologically safe for human consumption, reporting lower microbiological values​​than those foreseen by official regulation. The overall sensory evaluation indicates that the two formulations did not present statistically significant differences regarding the analyzed attributes, being the averages between “liked very much” and “moderately liked”. However, considering the group of cereal bars consumers, the formulation sweetened with pretreated leafs (F1) was found more than twice the acceptance regarding to the formulation sweetened with the leaf in natura (F2). These results demonstrate a viable option of a diet food product naturally sweetened.