Background: Immune checkpoint inhibitors (ICIs) are a novel class of immunotherapy used for the treatment of a variety of cancer types, most notably cancer of the lung and melanomas. Treatment with ICIs have been demonstrated to alter the metabolism and homeostasis management of lipids and glucose. Such signalling pathway interruptions can lead to an increased risk of serious cardiovascular diseases. However, baseline factors associated with this increased risk have not been robustly described in current literature. In this study, we determine baseline risk factors associated with cardiovascular disease hospitalisations in patients treated with ICIs for their cancer. Methods and Results: We retrospectively collected data for all patients treated with ICIs — including nivolumab, ipilimumab, pembrolizumab, tislelizumab, durvalumab, and atezolizumab — between 1st January 2010 and 1st January 2020 at the Hunter New England Local Health District. Patient medical history and demographic information up until 31st December 2022 were obtained through hospital electronic medical records. Outcome data was obtained from the Institutional Cardiac and Stroke Outcomes Unit database. Cardiac admission was defined as cardiac disease based on International Statistical Classification of Diseases and Related Health Problems 10th Revision, which included cardiac valve disease, hypertensive heart disease with (congestive) heart failure, hypertensive heart and renal disease, ischaemia (including atherosclerotic cardiovascular disease), pulmonary hypertension and heart disease, cardiomyopathy, heart block, arrhythmias, heart failure. Admissions were coded according to principal or any other diagnosis during any episode in admission after the commencement of ICI. Thus far, a total of 301 patients (mean age 67 years, males n = 187 (62.1%)) treated with ICIs have been analysed. N = 96 patients had a recorded hospital admission for a cardiac-associated event. Pre-existing arrhythmia (p = 0.043), heart failure (p = 0.006), and ischaemia (p = <0.001) were all significantly associated with increased cardiac admissions. Older age at first dose of ICI (p = 0.023) was also a contributor to cardiac hospitalisations. Conclusions: Preliminary results from our study identify patients with pre-existing cardiovascular disease risk factors are at an increased risk of cardiovascular hospitalisations because of their cancer treatment with ICIs. Adequate cardiovascular disease risk modification during treatment with ICIs may be necessary to reduce cardiovascular hospitalisations.