Inflammation and oxidative activities within the gut play major roles in the pathogenesis of ulcerative colitis (UC). We aimed to determine the effect of Melissa officinalis, an antioxidant and anti-inflammatory agent, on the colon histological characteristics in acetic acid (AA)-induced UC in rat models. Thirty-six male rats with AA-induced colitis were divided into 5 groups: no treatment (AA); daily treatment with 300 mg/kg Melissa officinalis orally (MO) and rectally (MR); and 100 mg/kg mesalamine orally (AO) and rectally (AR). Macroscopic and histopathological evaluation of the colon, along with a biochemical laboratory evaluation, were performed 10 days after UC induction. All treatment groups demonstrated lower macroscopic grading scores compared to the AA group. After treatment with MO, 42.9% of cases demonstrated no macroscopic changes, while 14.3% demonstrated only mucosal erythema. In the MR group 28.6% of rats had no changes in their mucosal lining and 28.6% had only mucosal erythema. Following histopathological evaluation, the AO group had lower scores regarding the severity of ulcer, inflammation, destruction, crypt abscess, and disorganization compared to the MO group. (P=0.02) The MR group demonstrated lower microscopic scores compared to the MO group, and also lower macroscopic scores compared to the AR group, although not significantly (P>0.05). Both oral and topical administration of Melissa officinalis have satisfactory healing properties compared to mesalamine, with topical route having better results. Therefore, further studies are needed to establish the benefit of Melissa officinalis administration (both orally and topically) within a UC treatment protocol.