Objective: To observe the occurrence of immune-related adverse events (irAEs) in the clinical application of programmed cell death protein-1 (PD-1), an immune checkpoint inhibitor (ICIs). Methods: A retrospective study was conducted on irAEs in 65 patients with malignant tumor who received PD-1 treatment in our hospital from January 2020 to December 2021, and their clinical characteristics and related blood test data were analyzed. Results: Among the 65 cancer patients, 28 cases (43.07%) had irAEs. A total of 35 adverse reactions occurred, including 2 cases (5.71%) of grade 3 and 4 irAEs. The most common irAEs were skin diseases (34.29%), many of which were skin rashes with itching. There was no statistically significant difference between the occurrence of irAEs and the patient’s gender composition, age, blood routine (hemoglobin, white blood cell count, platelet count, etc.) and liver function (P>0.05), but there was a significant correlation with the tumor type (P<0.05). Conclusion: PD-1 has a high safety in tumor treatment, and irAEs above grade 3 are rare. Close monitoring should be done in clinical application to achieve early detection, intervention and treatment, and control irAEs at a lower level to ensure the safety of clinical application of PD-1 and improve the survival time and treatment benefits of tumor patients.