ObjectiveTo highlight the incidence and management of acute coronary syndrome (ACS) in patients with gastric cancer undergoing immune checkpoint inhibitor (ICI) therapy, emphasizing the need for early detection and intervention in this high‐risk population.Patients and methodsWe presented a case of a 71‐year‐old male patient with poorly differentiated adenocarcinoma of the gastric antrum, clinical stage cT4N2M0, phase III, with no prior history of chronic diseases or cardiovascular risk factors. The patient was treated with a combination of ICI therapy (sintilimab) and chemotherapy using the albumin‐bound paclitaxel combined with S1 regimen. Following therapy, he developed symptoms and diagnostic findings consistent with ACS, which was managed with percutaneous coronary stenting.ResultsThe patient's presentation with ACS during ICI therapy underscored the potential cardiovascular risks associated with cancer treatments, particularly in patients without traditional cardiovascular risk factors. Management involved collaboration between oncologists and cardiologists, leading to successful coronary stenting and continuation of antitumor therapy.ConclusionACS is a significant risk in patients with malignancies undergoing ICI therapy, even in those without prior cardiovascular disease. Early recognition and management of ACS in this context are crucial to enable the continuation of cancer treatment and improve patient outcomes. This case underscores the importance of interdisciplinary collaboration in managing complex patients with concurrent cancer and cardiovascular disease.