Objective In this study, we aimed to determine the incidence of adverse drug reactions (ADRs) of atezolizumab, identify ADR signals that are significantly related to atezolizumab, and provide a reference for the rational use of atezolizumab in the clinic through the statistical analysis of its adverse drug events (ADEs) reported in the American Food and Drug Administration (FDA) Adverse Event Reporting System (FAERS) database. Methods In total, 4796 cases of atezolizumab ADEs reported in the American FAERS database from 2017 to 2019 were retrospectively analyzed. Results The top three ADEs were febrile neutropenia (3.7％), anemia (2.9％), and acute renal failure (2.3％). In addition, the incidence rates of some ADEs were significantly different according to sex and age. The systematic organ classification of atezolizumab ADEs involved 32 systems, among which the top three were blood and lymphatic system disorders (585 cases, 12.2％), gastrointestinal disorders (433 cases, 9.0％), and infections and infestations (401 cases, 8.4％). The reporting odds ratio (ROR) method was used to detect the ADR signals of atezolizumab. The ROR (95％ confidence interval) of the top ADE, febrile neutropenia, was 39.236 (33.757–45.604). In addition, we found 121 cases of complications associated with immune-related ADEs. Conclusion The ADRs of atezolizumab reported in the FAERS database were consistent with those mentioned in the instructions for atezolizumab use, suggesting that atezolizumab has an acceptable and controllable drug effect.