Atezolizumab is an anti-PD-L1 immune checkpoint inhibitor recommended for the treatment of locally advanced or metastatic urothelial carcinoma (mUC) after prior platinum-containing chemotherapy, regardless of PD-L1 status, among other treatment settings. We conducted a long-term follow-up to the exploratory analysis of overall survival (OS) and safety for the IMvigor211 intent-to-treat (ITT) population. Patients with mUC and disease progression during or following platinum-based chemotherapy were randomised 1:1 to receive atezolizumab 1200 mg or chemotherapy (vinflunine 320 mg/m2, paclitaxel 175 mg/m2, or docetaxel 75 mg/m2 according to investigator choice) intravenously every 3 wk. Although the primary analysis did not demonstrate statistically significant longer OS for patients receiving atezolizumab versus chemotherapy, updated OS showed long-term durable remission. With a median of 33 mo of follow-up, the 24-mo OS rate was 23% with atezolizumab and 13% with chemotherapy. Safety findings were consistent with the primary analysis, with no new signals detected. Chemotherapy-treated patients experienced more grade 3/4 treatment-related adverse events (AEs; 43% vs 22%) and more AEs leading to treatment discontinuation (18% vs 9%). Atezolizumab-treated patients experienced more AEs of special interest (35% vs 20%), which tended to be grade 1-2. Our findings support the use of atezolizumab in platinum-treated patients with mUC regardless of PD-L1 status. PATIENT SUMMARY: We report follow-up results from a study of an immunotherapy treatment, atezolizumab, in patients with bladder cancer who had already received platinum-containing chemotherapy. This analysis compared the effectiveness of atezolizumab with chemotherapy over 2.5 years after starting treatment. The results show that patients who received atezolizumab lived longer and had manageable side effects compared with patients who received chemotherapy. This trial is registered at ClinicalTrials.gov as NCT02302807.