Glucose-mediated oxidative stress and upregulation of cyclooxygenase (COX)-2 pathway activity have been implicated in the pathogenesis of several vascular complications of diabetes including diabetic neuropathy. However, in non-diabetic subjects the cardiovascular safety of selective COX-2 inhibition is controversial. The aim of this study was to explore the links between hyperglycemia, oxidative stress, activation of the COX-2 pathway, cardiac sympathetic integrity and the development of left ventricular (LV) dysfunction in experimental diabetes. R-R interval and parameters of LV function measured by echocardiography using 1% isoflurane, LV sympathetic nerve fiber density, LV collagen content and markers of myocardial oxidative stress, inflammation, and prostaglandins content were assessed after 6 months in control and diabetic COX-2 deficient (COX-2^-/-) and littermate, wild-type (COX-2^+/+) mice. There were no differences in blood glucose, LV echocardiographic measures, collagen content, sympathetic nerve fiber density and markers of oxidative stress and inflammation between nondiabetic (ND) COX-2^+/+ and COX-2^-/- mice at baseline and thereafter. After 6 months, diabetic COX-2^+/+ mice developed significant deteriorations in the R-R interval and signs of LV dysfunction. These were associated with a loss of LV sympathetic nerve fiber density, increased LV collagen content, and a significant increase in myocardial oxidative stress and inflammation as compared with ND mice. Diabetic COX-2^-/- mice were protected against all these biochemical, structural, and functional deficits. These data suggests that in experimental diabetes, selective COX-2 inactivation confers protection against sympathetic denervation and LV dysfunction by reducing intramyocardial oxidative stress, inflammation and myocardial fibrosis.