PURPOSE: Patients treated with bladder-preserving therapy for muscle-invasive bladder cancer are at risk of developing recurrent nonmuscle-invasive bladder cancer. This study aims to describe the efficacy and adverse events of postoperative Bacillus Calmette-Guerin (BCG) instillation in patients with superficial recurrence following bladder-preserving therapy for muscle-invasive bladder cancer. METHODS: We retrospectively analyzed 120 patients diagnosed with nonmuscle-invasive bladder cancer who underwent transurethral resection followed by BCG instillation. The 19 patients with prior muscle-invasive bladder cancer were categorized as the NMIBC-M group, while the remaining 101 patients formed the NMIBC group. All patients completed a 6-cycle BCG course. RESULTS: Both groups showed no significant differences in baseline characteristics, except for the number of BCG instillations (15.5 vs. 9, P = 0.010). Between NMIBC and NMIBC-M group, 5-year overall survival were 87.4% and 75.8%, respectively. And the 5-year recurrence-free survival were 57.0% and 66.7%, respectively. The Kaplan-Meier curve of overall survival and recurrence-free survival showed on statistical significance in both groups. Adverse effects were also comparable between groups. However, patients in the group with prior muscle-invasive bladder cancer reported lower rates of urinary retention (28.7% vs. 0.0%, P = 0.017) and fever (30.7% vs. 5.3%, P = 0.044). CONCLUSIONS: No significant differences of efficacy and side effects were observed for postoperative BCG instillation between the patients with superficial recurrence following bladder-preserving therapy for muscle-invasive bladder cancer and those without muscle-invasive bladder cancer history. Prospective study in the future should be carried out for further confirmation.