BACKGROUND: The therapeutic potential of nifuroxazide in colitis has been explored in several experimental studies of ulcerative colitis (UC). AIM: To evaluate the efficacy of nifuroxazide in patients with UC. METHODS: Fifty patients with mild to moderate UC were randomly assigned into two groups (n = 25 each). The placebo group received a placebo alongside mesalamine (1 g three times daily [t.i.d.]) for six months. The nifuroxazide group received nifuroxazide (200 mg twice daily) in combination with mesalamine (1 g t.i.d). A gastroenterologist assessed disease severity using the partial Mayo score (PMS). Serum levels of C-reactive protein (CRP), nuclear factor kappa B (NF-kappaB), interleukin-6 (IL-6), and signal transducer and activator of transcription 3 (STAT3) were measured before and after treatment. Quality of life was evaluated using the Inflammatory Bowel Disease Questionnaire (IBDQ-32). Primary outcomes: Change in PMS. Secondary outcomes: change in IBDQ-32 and in the level of measured biomarkers. RESULTS: Baseline measurements were comparable between groups (p > 0.05). Post-treatment values showed significant improvements within both groups compared to baseline. However, the nifuroxazide group demonstrated significantly greater improvements than the placebo group, including reductions in PMS (p = 0.005) and increases in IBDQ scores (p = 0.002). Additionally, significant decreases were observed in IL-6 (p = 0.03), NF-kappaB (p = 0.03), CRP (p = 0.02), and STAT3 (p = 0.03) levels. The placebo group had a response rate of 56% (14/25) and a remission rate of 24% (6/25), whereas the nifuroxazide group achieved a response rate of 76% (19/25) and a remission rate of 56% (14/25), based on PMS. CONCLUSION: Co-administration of nifuroxazide with mesalamine improved clinical outcomes, including higher response and remission rates, reduced inflammation by reducing IL-6/STAT3, and enhanced quality of life in patients with UC, compared to mesalamine alone. TRIAL REGISTRATION IDENTIFIER: NCT05988528.