The current first-line standard treatment for advanced small cell lung cancer (SCLC) is a combination of chemotherapy and immunotherapy. However, few efficacy data are available in a real-life settings, including frail patients. The aim of this study is to describe the real-life efficacy of chemoimmunotherapy in an unselected SCLC population. We conducted a retrospective multicenter study, which compared two cohorts of patients with treatment-naive metastatic SCLC treated in six academic centers in the Greater Paris area. Cohort 1 included patients treated with chemotherapy between January 2017 and December 2018, and cohort 2 included patients treated with chemoimmunotherapy between January 2019 and December 2020. A total of 153 consecutive patients were included (cohort 1: n = 96; cohort 2: n = 57). Clinical characteristics were similar between the two cohorts. Overall survival (OS) was statistically higher in cohort 2 (median survival 15.47 months) than in cohort 1 (median survival 9.5 months) (p = 0.0001). OS for patients with a performance status ≥2 and for patients ≥70 years old was not statistically different between the two cohorts. Chemoimmunotherapy efficacy was better compared to chemotherapy alone in case of brain or liver metastases. In conclusion, the combination of chemoimmunotherapy in metastatic SCLC appears to provide a real-life OS benefit. Dedicated clinical trials are needed to test this strategy in patients with impaired performance status or advanced age.