Platelet to lymphocyte ratio (PLR) is a haematological biomarker which increases with inflammation and vascular oxidative stress. Many studies have explored the role of inflammatory pathways in the development and progression of coronary artery disease (CAD). This study sought to investigate the previously known positive association between PLR and CAD and validate it our cardiothoracic surgery patients. A total of 768 patients undergoing coronary angiography at St Vincent’s Hospital Melbourne were analysed between May 2012 and December 2019. 528 (69%) patients were found to have CAD. CAD was defined as >50% stenosis in one or more coronary arteries. PLR was associated with CAD (p=0.001) on bivariate analysis. PLR remained significantly associated after adjusting for traditional cardiovascular risk factors (OR 0.996; p=0.037) in multivariate logistic regression. Additionally, the results showed increasing age (OR 1.02; p=0.054), male gender (OR 3.08; p<0.001), smoking (OR 1.605; p=0.031), hypertension (OR 2.153; p=0.002), increasing HbA1c (OR 1.784; p<0.001), total cholesterol (OR 0.665; p<0.001) and increasing TG:HDL ratio (OR 1.671; p<0.001) also independently correlated with CAD. PLR was not significantly associated with congestive heart failure and aortic stenosis. PLR was inversely correlated with angiographic CAD. These results are in contrast with previous studies showing a higher PLR to be associated with CAD. Further investigation of this association is warranted.