Although several studies have demonstrated that cardiac diastolic function is impaired but cardiac systolic function is preserved with aging, no large-scale analysis of cardiac function by echocardiography in subjects aged ≥ 90 years exists. The purpose of the present study was to elucidate the cardiac structure and function in the oldest old in order to assess the effect of aging on cardiac function. Echocardiographic examination was performed in 1793 subjects who were in their fifties, sixties, seventies, eighties, and nineties. Left ventricular (LV) wall thickness and dimension were measured by M-mode echocardiography. LV ejection fraction (LVEF) was calculated and used as the parameter representing LV systolic function. LV diastolic function was assessed using the peak velocity of early rapid filling (E velocity) and the peak velocity of atrial contraction (A velocity), and the ratio of E to A (E/A) by the transmitral flow. The Tei index, which reflects both LV diastolic and systolic function, was also calculated. The E/A decreased progressively with aging, and demonstrated the closest correlation with age among all the indexes of cardiac function (r = -0.44, P < 0.001). In contrast, LVEF and the Tei index demonstrated a very weak correlation with age (r = -0.13, P < 0.001 and r = 0.16, P < 0.001, respectively). The mean value for LVEF remained normal with aging in all age strata (50s: 71 ± 8%, 60s: 71 ± 8%, 70s: 70 ± 9%, and 80s: 71 ± 10%), but decreased significantly in subjects in their 90s (66 ± 10%, P < 0.001). In addition, the mean value for the Tei index also remained normal with aging in subjects in their 50s (0.35 ± 0.10), 60s (0.38 ± 0.14), 70s (0.38 ± 0.12), and 80s (0.39 ± 0.15), but showed an abnormal value in subjects in their 90s (0.45 ± 0.12, P < 0.001). In conclusion, both diastolic dysfunction and systolic dysfunction with advancing age were observed in the oldest old aged ≥ 90 years. The age-related impairment of systolic function as well as diastolic function should be considered when echocardiography is used to evaluate the causes of heart failure in the oldest old.