The aim of this study was to determine the effects of a short-term high-intensity exercise program on diastolic function and glucose tolerance in obese individuals with and without metabolic syndrome (MetSyn). Obese men and women (BMI > 30 kg/m2; 39–60 years) with and without the MetSyn (MetSyn 13; non-MetSyn 18) underwent exercise training consisting of 10 consecutive days of treadmill walking for 1 h/day at 70–75% of peak aerobic capacity. Subjects performed pre- and post-training testing for aerobic capacity, glucose tolerance (2-h meal test), and standard echocardiography. Aerobic capacity improved for both groups (non-MetSyn 24.0 ± 1.6 ml/kg/min vs. 25.1 ± 1.5 ml/kg/min; MetSyn 25.2 ± 1.8 ml/kg/min vs. 26.2 ± 1.7 ml/kg/min, P < 0.05). Glucose area under the curve (AUC) improved in the MetSyn group (1,017 ± 58 pmol/l/min vs. 883 ± 75 pmol/l/min, P < 0.05) with no change for the non-MetSyn group (685 ± 54 pmol/l/min vs. 695 ± 70 pmol/l/min). Isovolumic relaxation time (IVRT) improved in the MetSyn group (97 ± 6 ms vs. 80 ± 5 ms, P < 0.05), and remained normal in the non-MetSyn group (82 ± 6 ms vs. 86 ± 5 ms). No changes in other diastolic parameters were observed. The overall reduction in IVRT was correlated with a decrease in diastolic blood pressure (DBP) (r = 0.45, P < 0.05), but not with changes in glucose tolerance. Body weight did not change with training in either group. A 10-day high-intensity exercise program improved diastolic function and glucose tolerance in the group with MetSyn. The reduction in IVRT in MetSyn was associated with a fall in blood pressure. These data suggest that it may be possible to reverse early parameters of diastolic dysfunction in MetSyn with a high-intensity exercise program.