To investigate the effect of anti-cytokine-based therapy in the course of diabetic cardiomyopathy, we performed a study using an anti-TNF-α monoclonal antibody treatment (mab) in Sprague male Dawley (SD) rats with streptozotocin-induced diabetic cardiomyopathy. Five days after streptozotocin injection, rats were treated with the anti-TNF-α mAb C432A for 6 weeks.At the end of the study, left ventricular (LV) function was determined by a pressure-catheter. Intercellular adhesion molecule (ICAM)-1, vascular adhesion molecule (VCAM)-1, β2-lymphocyte-integrins⁺ (CD18⁺, CD11a⁺, CD11b⁺), ED1/CD68⁺ and cytokine (TNF-α, interleukin (IL)-1β)- expressing infiltrates, total collagen content and stainings of collagen I and III were quantified by digital image analysis. LV phosphorylated and total ERK protein levels were determined by Western Blot. TNFα-antagonism reduced ICAM-1- and VCAM-1 expression and leukocyte infiltration to levels of non-diabetics and decreased macrophage residence by 3.3-fold compared with untreated diabetics. In addition, anti-TNF-α mAb-treatment decreased diabetes-induced cardiac TNF-α and IL-1β expression by 2.0-fold and 1.8- fold, respectively, and reduced the ratio of phosphorylated to total ERK by 2.7-fold. The reduction in intramyocardial inflammation was associated with a 5.4-fold and 3.6-fold reduction in cardiac collagen I and III content, respectively. This was reflected by a normalization of cardiac total collagen content to levels of non-diabetics and associated with an improved LV function. TNFα-antagonism attenuates the development of experimental diabetic cardiomyopathy associated with a reduction of intramyocardial inflammation and cardiac fibrosis.