Small cell lung cancer (SCLC) is a very aggressive and proliferative disease, with little progress being having made for its treatment in decades. Our goal was to evaluate the effect of immune checkpoint inhibitors (ICIs) and identify optimal first-line interventions for the treatment of SCLC. A systematic literature search of the Cochrane Library, PubMed and oncology conference proceedings were conducted. Randomized trials evaluating ICIs for SCLC were included. We use the risk of bias tool in RevMan 5.3 to assess the quality of studies. We used Stata version 15.0 to carry out data direct comparison and R version 4.0.2 to conduct the Bayesian network analysis. A total of 16 relevant clinical trials comprising 4,476 patients were included. We found the magnitude of efficacy for ICIs as first-line therapy conferred a statistically significant benefit in overall survival (OS) and progression-free survival compared to chemotherapy alone. The results were 0.82 (95% CI, 0.76-0.89, P<0.001) and 0.80 (95% CI, 0.74-0.86, P<0.001). For objective response rate (ORR), the result (1.13, 95% CI, 0.97-1.31, P=0.109) was not significant. In the second-line and maintenance treatment, no additional benefit was observed. With regard to safety, results showed that for all grades of AEs and grades 3-4 AEs, the pooled results were 1.36 (95% CI: 0.50-3.70; P=0.543) and 1.35 (95% CI: 0.58-3.15; P=0.484) respectively. In addition, the indirect comparison results showed that nivolumab combined with chemotherapy led to the most significant improvement in OS, while durvalumab combined with chemotherapy was a more efficacious therapy for improving ORR compared with the other interventions; the probability were the best treatments was 73.93% and 81% respectively. Our results showed ICIs combined with etoposide and platinum-based drugs as first-line treatment of SCLC have benefits for patients and there was no evidence of a significant difference in efficacy among the different ICI drugs used for the first-line therapy. As for toxicity, the ICIs did not increase the frequency AEs for patients. However, as some studies are ongoing and the full data have still not been reported, our conclusions may not be completely representative. 2021 Annals of Translational Medicine. All rights reserved.