Background: Anti-PD-L1 blockades plus EP is the standard first-line therapy for ES-SCLC from IMpower133 and CASPIAN. Subgroup analyses of the two trials indicated that patients (pts) without BMs could benefit from atezolizumab and durvalumab, while those with BMs could not. The aim of the retrospective study is to further investigate the clinical efficacy of the first-line anti-PD-L1 blockades plus EP for ES-SCLC with BMs. Methods: Between 2017 and 2021, pts with newly diagnosed ES-SCLC and baseline BM confirmed by CT or MRI at Shandong Cancer Hospital and Institute were enrolled. According to whether combined with anti-PD-L1 blockades (atezolizumab or durvalumab) or not, pts were assigned to anti-PD-L1+EP group and EP group, respectively. Response was assessed by RECIST 1.1 and survival analyses were conducted using Kaplan-Meier and log-rank tests. Results: A total of 56 pts were enrolled in the current study. Eighteen pts were allocated to anti-PD-L1+EP group and 38 were allocated to EP group. The median follow-up time was 18.17 months. Overall response rate (ORR) was 72.22% vs 78.95% (P= 0.83) and disease control rate (DCR) was 100% vs 97.37% in the two groups, respectively. And for BMs, the intracranial ORR and DCR were 50.00% vs 68.42% (P= 0.18) and 72.22% vs 78.95% (P= 0.83), respectively. Progression-free survival (PFS) was numerically prolonged with anti-PD-L1 blockades, but the significance was not achieved (median: 9.4m vs 7.3m, P = 0.146, HR = 0.63 (95%CI, 0.35-1.13)). The intracranial PFS was not improved, neither (median: 8.2m vs 7.9m, P= 0. 943, HR = 1.02 (0.53-2.00)). However, overall survival was significantly prolonged with anti-PD-L1 blockades (median: NR vs 15.53m, P = 0.012, HR = 0.20 (0.09-0.46)). Conclusions: Collectively, we found that the addition of the first-line anti-PD-L1 blockades to EP brought about a significant survival benefit compared with EP alone for ES-SCLC with BMs.