Diabetic cardiomyopathy is a common chronic complication leading to heightened risk of heart failure among diabetic patients. In this chapter, we describe the methods for maintenance and breeding of two diabetic animal models, OVE26 and Agouti mice, for type 1 and type 2 diabetes, respectively. To understand the pathological mechanism, antioxidants such as manganese superoxide dismutase are overexpressed specifically in hearts of diabetic mice. Methods utilized to produce cardiac-targeted transgenic mice are presented in this chapter. Diabetic cardiomyopathy is evaluated in control, diabetic and transgene-protected diabetic animals by measuring contractility of isolated cardiomyocytes. Preparation and contractile analysis of cardiac myocytes are described in detail. Diabetic cardiomyocytes exhibit impaired contractility as well as delayed relaxation, and cardiac-overexpressed antioxidant transgenes are shown to reverse this damage.