The aim of this study was to evaluate the effect of the combination of bacillus Calmette-Guerin (BCG) and mitomycin C (MMC) in comparison to BCG alone in the treatment of patients with non-muscle invasive bladder cancer. Materials and methods: Our study is a randomized clinical trial carried out on 50 Patients diagnosed with non-muscle invasive urothelial bladder cancer, they were classified into 2 groups: Group (I): included 25 patients who received immediate single instillation of mitomycin C (MMC) after TURBT then intravesical BCG per week for 6 weeks and Group (II): included 25 patients who were treated with TURBT followed by intravesical BCG per week for 6 weeks alone (standard of care). Patients were being followed up at 3, 6, 12, 18 months by cystoscopy. The outcome measures were time to recurrence, progression of the disease to muscles or other organs, disease free survival, and treatment-related side effects. Result: Immediate single instillation of mitomycin C (MMC) after TURBT in combination with BCG had low recurrence rate compared to BCG alone (36% vs 48% respectively, p=0.567), and longer disease free interval (64.0% vs 52.0% respectively, p=0.567). Four patients progressed to muscle invasive bladder cancer in BCG alone group. While three patients progressed to muscle invasive bladder cancer in MMC+BCG group However, this difference was not statistically significant (p= 0.896). Regarding side effects, there were no statistically significant differences between groups. Conclusion: Immediate single instillation of mitomycin C after TURBT in combination with BCG seems to be effective in decrease recurrence rates and enhances the disease-free interval compared with TURBT followed by BCG alone at least in short term.