ABSTRACT Background: Vitamin D is a necessary hormone in many tissues including cardiac myocytes. The autocrine and paracrine regulation of cellular growth differentiation and function in several organs depends on it through preventing the activation of the heart’s renin-angiotensin system and natriuretic peptides vitamin D regulates calcium Flux, extracellular matrix turnover and myocardial contractility. Our study aimed to identify the relationship between vitamin D deficiency and myocardial function (both systolic and diastolic) in medical staff with an adverse history of cardiac disease and normal transthoracic echo Doppler parameters. Methods: A comparative cross-sectional study involved 80 doctors, nurses, and technicians working at Zagazig University Hospitals; they were divided into two groups based on 25(OH) D levels: Group A (n=40) had a low vitamin D level of <20 ng/mL & Group B (n=40) had an average vitamin D level (>20 ng/ml). Both groups were subjected to conventional echocardiography and tissue Doppler imaging. Results:The study found significantly higher Left ventricular and right ventricular Tei index in group A compared to group B (P value =0.01 and ˂0.001), respectively We also found a significantly higher tricuspid deceleration time (DT (t)), tricuspid lateral A' and significantly longer tricuspid interventricular isovolumetric relaxation time (IVRT(T) in group A compared to group B. Finally, a receiver operating characteristic (ROC) c urve was performed which showed that 25(OH) D less than 19.5 was found to have 83% sensitivity and 65% specificity in determining a high RV tei index (>0.55).Conclusions: Our study showed that Vitamin D deficiency affects both the systolic and diastolic function of the heart. Keywords: Vitamin D, Cardiac function, Tissue Doppler imaging, TEI index