Abstract: Objective To explore the effect of antibiotics on advanced esophageal cancer patients receiving immune checkpoint inhibitors (ICIs).Methods The clinical data of advanced esophageal cancer patients who received ICIs from January 2020 to September 2022 in the Affiliated Hospital of Xuzhou Medical University were retrospectively analyzed. According to the use of antibiotics,the patients were divided into two groups: an antibiotic group and a non-antibiotic group, and their survival was follow-up visited.Results A total of 136 advanced esophageal cancer patients were included in the study, including 65 patients in the antibiotic group and 71 in the non-antibiotic group. There were no statistical differences in gender, age, and clinical stage between the two groups (P<0.05). However, patients treated with antibiotics showed shortened median overall survival (mOS) and median progression-free survival (mPFS) (P<0.05). Multivariate analysis indicated that treatment scheme was an independent risk factor for prognosis.According to subgroup analysis, quinolones and aminoglycosides did not exhibit remarkable effect on mOS and mPFS (P>0.05), while β-lactams shortened mOS and mPFS in patients (P<0.05). Conclusions Antibiotics can affect the efficacy of ICIs. Different types of antibiotics exhibit various effect on clinical outcomes. Furthermore, β-lactams should be avoided in patients with advanced esophageal cancer who are undergoing or planning to undergo ICIs.