It is well established that maximal cardiac output declines with advancing age. Age-related decline in cardiac output could result from changes in either systolic or diastolic function that are also apparent at rest. We investigated the effects of age on systolic and diastolic function in male and female mice. Mice were studied at 4-7months and 17-20 months. Echocardiography was performed with FujiFilm Visual Sonics VevoF2 to obtain ejection fraction, fractional shortening, and E/A ratio. In male mice, fractional shortening decreased by 25% (young: 31.26±1.24, old: 23.31±1.82, P=0.002 young v. old) and ejection fraction decreased by 19.77% (young: 58.23±1.63, old: 46.71±3.05, P=0.002 young v. old) with age. In female mice, fractional shortening and ejection were stable with age. E/A decreased with age in both male (young: 1.53±0.09, old: 1.18±0.07, P=0.02 young v. old) and female (young: 1.64±0.08, old: 1.28±0.07, P=0.002 young v. old) mice. These data indicate that systolic function declines with age in male, but not female mice. In contrast, diastolic function declines with age in both male and female mice. Further analysis is needed to determine how these changes in resting cardiac function correlate with changes in exercise capacity in male and female mice. NIH R01HL166591. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.