Bacillus Calmette-Guérin (BCG) therapy for patients with non-muscle invasive bladder cancer (NMIBC) faces limitations in efficacy and significant side effects, aggravated by a recent global shortage. In this prospective clinical study, we report outcomes of sequential intravesical adminis-tration of gemcitabine and docetaxel (Gem/Doce) as the first-line treatment in BCG-naïve patients with high-risk NMIBC (HR NMIBC). From October 2019 until April 2022, we enrolled 52 patients and followed treatment protocol set by the University of Iowa. Follow-up assessments were con-ducted every 3 months. In this cohort, 25 (48.1%) patients were diagnosed with T1HG bladder cancer, 10 (19.2%) patients had carcinoma in situ (CIS), and 17 (32.7%) patients had a combination of CIS+T1HG. Median time to first recurrence in T1HG, CIS and T1HG+CIS groups was 11, 10.5 and 8.8 months, respectively. The recurrence-free survival was 98.1%, 94.2% and 80.8% at 6, 9 and 12 months, respectively. The rate of progression-free survival was 100%, 98.1% and 92.3% at 6, 9 and 12 months, respectively. We demonstrated the safety and efficacy of Gem/Doce therapy in BCG-naïve patients with HR NMIBC during a one-year follow-up. Further research with extended follow-up, as well as direct comparison of Gem/Doce and other anticancer agents, are essential.