Diabetes is associated with impaired cardiac energetics and diastolic dysfunction. A substrate shift toward ketones has been proposed to explain the benefits of empagliflozin on cardiovascular outcome in diabetes patients. We investigated the effects of empagliflozin on cardiac energetics and function in diabetic db/db mice using 31P-MRS and MRI. After a single dose of empagliflozin, cardiac PCr/ATP ratio was higher compared with placebo-treated controls, which was associated with increased plasma ketone levels and lower cardiac load. After 6 weeks of treatment, cardiac diastolic function tended to be improved, while plasma ketones and cardiac PCr/ATP ratio were not different from placebo.