Background: The left atrium (LA) is much more than simply a conduit for left ventricular (LV) filling, and its size and remodeling are recognized as a predictor of poor outcomes in multiple disease states. LA function is a surrogate marker of LV diastolic dysfunction. Objective: To assess left atrial function in coronary artery disease patients with preserved left ventricle ejection fraction, with and without left atrial expansion by three dimensional speckle tracking echocardiograghy. Patient and methods: Fifty patients with chronic coronary syndrome were divided according to left atrial dilation into two groups high risk group where left atrial dilation was more than 4cm (8 males and 8 females)  and  low risk group where left atrial dilation was less than 4 cm (18 males and 16 females) in addition to 20 healthy individual as control group (7 males and 13 females) who presented to the Cardiology Department at Al-Hussain University Hospital and Al-Azhar Islamic Center for elective coronary angiography from May 2019 to June 2020. Results: There was a statistically significant increase in control group in comparison to low risk and high risk. The LA peak ventricular systolic area strain (ASs %) in patients group was significantly lower than in the control group, whereas in the low risk group was significantly higher than in the high risk group. The LA peak pre-atrial contraction area strain (ASa %) in patients group was significantly lower than in the control group, whereas in the low risk group was significantly higher than in the high risk group. Conclusion: Three-dimensional speckle tracking echocardiography represented a non-invasive, relatively simple and reproducible technique to assess left atrial myocardial function in patients with chronic coronary syndrome.