Background: Diabetes mellitus a major factor that has adverse effects on the vascular system and the heart. It causes an increase in cardiac muscle thickness, resulting in decreased compliance and increased peripheral arterial stiffness. This study aims to assess the left ventricular mass (LVM) and left ventricular hemodynamic changes in diabetic patients measured by Doppler echocardiography. Patients and Methods: The study included 50 diabetic patients ranging in age between 25 and 80 years, (mean age: 54.1 ± 15.10, 19 males, 31 females) and 50 healthy subjects, aged 25 to 80 years (mean age: 48.52 ± 14.45, 11 males, 39 females). Doppler echocardiography was used to assess left ventricular function. The measurements included posterior wall thickness at diastole (PWTd), interventricular septum thickness at diastole (IVSTd), left ventricular diameter at the end of diastole (LVIDd), left ventricular diameter at the end of systole (LVIDs), peak velocity at atrial contraction (A), early peak velocity (E), left ventricular ejection fraction (LVEF%), left ventricular mass (LVM), and relative wall thickness (RWT). Results: The data showed that changes in E/A differences between diabetic patients and controls for age ranges 25 to 50 and 60 to 80 years were -24.60% and -31.93% (p < 0.05). There were non-significant differences in the LVIDd/LVIDs ratio between diabetic patients and controls for both age groups: 1.31% and 6.25%, respectively. For 25- to 50-year olds, the changes in RWT and LVM were 50% and 74.43%, respectively (p < 0.05), while the differences in RWT and LVM for 60- to 80-year olds were 48.71% and 70.06%, respectively (p < 0.05). Conclusion: The results indicate that diastolic dysfunction may be higher in diabetic patients compared to healthy subjects, which may be due to adverse influence of diabetes on cardiac muscle. These changes in left ventricular structure may include LV hypertrophy, increase in stiffness, and reduction in compliance, with increase in left ventricular mass, relative wall thickness, posterior wall thickness at diastole, and interventricular septum thickness at diastole.