Nadofaragene firadenovec-vncg is a non-replicating adenoviral vector-based gene therapy for BCG-unresponsive carcinoma in situ (CIS) with/without HG Ta/T1). We report outcomes following 5 years of planned follow-up. This open-label phase 3 trial (NCT02773849) enrolled patients with BCG-unresponsive NMIBC in 2 cohorts: CIS ± Ta/T1 (CIS; n = 107) and Ta/T1 without CIS (Ta/T1 cohort; n = 50). Patients received 75 mL (3 × 10¹¹ vp/mL) of Nadofaragene firadenovec intravesically once every 3 months with cystoscopy and cytology assessments, with continued treatment offered to those remaining high-grade recurrence free (HGRF). One hundred fifty-seven patients were enrolled from 33 US sites (n = 151 included in efficacy analyses). Median follow-up was 50.8 months (IQR 39.1-60.0), with 27% receiving ≥ 5 instillations and 7.6% receiving treatment for ≥ 57 months. 5.8% (95% CI 2.2-12.2) of patients with CIS and 15% (95% CI 6.1-27.8) of patients with HG Ta/T1 were HGRF at month 57. Kaplan-Meier (KM)-estimated HGRF survival at 57 months was 13% (95% CI 6.9-21.5) and 33% (95% CI 19.5-46.6) in the CIS and Ta/T1 cohorts, respectively. Cystectomy-free survival at month 60 was 49% (95% CI 40.0-57.1): 43% (95% CI 32.2-53.7) in the CIS cohort and 59% (95% CI 43.1-71.4) in the Ta/T1 cohort. Overall survival at 60 months was 80% (71.0, 86.0): 76% (64.6-84.5) and 86% (70.9-93.5) in the CIS and Ta/T1 cohorts, respectively. Only 5 patients (4 with CIS and 1 with Ta/T1) experienced clinical progression to muscle-invasive disease. At 60 months, Nadofaragene firadenovec-vncg allowed bladder preservation in nearly half of the patients and proved to be a safe option for BCG-unresponsive NMIBC.