Abstract Background/Introduction Immune checkpoint inhibitors (ICI) have significantly improved outcomes for several malignancies. Despite these benefits, patients with cancer face an increased risk for the development of cardiovascular disease due to mutual risk factors, similar biological mechanisms, as well as cardiotoxic side effects of therapy. Therefore, there is a pressing need for effective risk stratification strategies. Purpose This study aimed to explore the association between NT-proBNP levels and the risk of acute cardiovascular hospitalizations and death in patients who receive ICI. Methods We used electronic health records of patients treated with ICI who had available baseline NT-proBNP levels at our hospital, a tertiary academic center, between January 2017 and July 2022. The primary outcome of interest was the composite of acute cardiovascular hospitalization or death. The associations between NT-proBNP and outcomes were analyzed using cox regression models adjusted for age, sex, serum creatinine, diabetes, HF, CAD, hypertension, AF, LDL-C, and CRP. Results In total, 550 patients (35% female, median age 65 yrs) were included in the study. The median NT-proBNP levels were 272 pg/mL (IQR 102-742 pg/mL) and 388 (71%) patients had NT-proBNP levels ≥125 pg/mL. During a median FU of 67 weeks, 190 patients (35%) died, and 103 CV hospitalizations occurred in 76 patients (14%). Compared with patients with NT-proBNP concentrations <125, those with NT-proBNP concentrations ≥125 pg/ml had significantly higher event rates of the combined endpoint (12-Month KM event rates: 38% vs 21%, P<0.001). After multivariable adjustment, NT-proBNP remained independently associated with an increased risk of cardiovascular hospitalization and death (Adjusted HR for 1-SD increase in log-transformed biomarker 1.64, 95% CI 1.24 to 2.14; Figure). Conclusion These data highlight NT-proBNP levels as a valuable marker for identifying patients at increased risk of cardiovascular complications during ICI therapy.