Diabetes mellitus (DM) and left ventricular dysfunction (LVD) are often coexistent and invariably associated with increased mortality. Data on long-term prognosis of “isolated” diastolic LVD in diabetics are lacking; therefore, we evaluated these prognostic implications in patients with peripheral arterial disease (PAD) and DM. Using echocardiography, 1321 patients were screened for diastolic, systolic (ejection fraction <50%) or combined LVD. Diastolic LVD was diagnosed based on the ratio of early rapid filling to late filling due to atrial contraction, pulmonary vein flow, and deceleration time. Patients using glucose-lowering drugs or insulin or with a fasting glucose level >6.1 mmol/L were diagnosed with DM. The primary end point was occurrence of cardiovascular death during a mean follow-up of 2.5 ± 1.9 years. In the total population, DM was diagnosed in 518 patients (39%), and diastolic, systolic, or combined LVD was present in 356 patients (27%), 102 patients (8%), or 156 patients (12%), respectively. In diabetic patients, diastolic and systolic LVDs were associated with increased cardiovascular mortality (hazard ratio 1.8, 95% confidence interval 1.03 to 3.03; hazard ratio 3.1, 95% confidence interval 1.46 to 6.38). In nondiabetic patients, the same association between diastolic or systolic LVD and outcome was observed (hazard ratio 2.2, 95% confidence interval 1.30 to 3.74; hazard ratio 3.9, 95% confidence interval 2.00 to 7.52). Combined systolic and diastolic LVD had the worst prognosis. In conclusion, diabetic patients with PAD have an increased prevalence of isolated systolic and combined LVD. In patients with PAD the presence of isolated diastolic, systolic, or combined LVD was independently and equally associated with increased cardiovascular mortality, irrespective of the concomitant presence of DM.