Objective: To test whether 2 sequential BCG-induction courses improve the response of high-risk non–muscle invasive bladder cancer. Achieving a complete response (CR) to BCG is critical to disease-free survival. Patients with preexisting BCG-specific immunity owing to prior exposure to BCG have longer disease-free survival than BCG-naïve patients likely due to heterologous immunity from the initial priming of the immune system. We evaluated this hypothesis in a phase II prospective clinical trial. Methods: From 2015 to 2018, we recruited patients with primary or recurrent NMIBC (high-grade Ta, T1 tumors, with or without CIS) to receive 2-induction courses (12 intra-vesical instillations) of BCG. The primary aim of the study was CR rate 6 months after start of the first BCG induction. CR was defined as no tumor at cystoscopy or TURB biopsy. No maintenance BCG was given. We targeted at least 75 evaluable patients, and a CR of 80% or better was deemed significant. Results: Eighty-one patients agreed to participate. Five withdrew before starting BCG, leaving 76 evaluable patients. Sixty-three patients (83%) completed the 12 instillations on schedule. Of these, 62 patients (91%) had a CR at 6 months. None of the patients had tumor progression. Serious adverse event was seen in 1 patient (1%). Recurrence-free survival at 2 years after complete response was 85% (95% CI 77%, 95%). Conclusion: The high response rate in patients with high-risk non–muscle-invasive bladder cancer justifies 2 BCG induction cycles in current practice.