This study aimed to investigate the effectiveness of a special gel composed of dried guava leaves for treating mouth ulcers. To formulate the herbal gel, different amounts of guava leaf powder were blended with a gel base made up of Carbopol 934 and propylene glycol to create a formulation for each concentration tested. After that, each formulated gel was evaluated for various characteristics. The compatibility between the components in the guava leaf powder and the polymer (the gel base) was verified with infrared spectroscopy. Furthermore, no chemical reaction occurred between the guava powder and the polymer component. The resulting gel was homogeneous and translucent with a pH value of 7-7.5. The gel was also easy to dispense when applied from its tube, which is a beneficial characteristic for any gel product. In addition, the gel formulation exhibited significant antifungal activity against the two fungal organisms tested (Aspergillus aures and Candida albicans). The flavonoids found in guava leaves help protect cells from oxidative stress caused by free radicals. Overall, the guava leaf gel was found to be superior to other commercial gels (in terms of tolerability) and was deemed both effective and successful for use in the preparation of an herbal formulation from dried guava leaves.