Abstract Diabetes is a major health problem associated with adverse cardiovascular outcomes. The apolipoprotein A‐I mimetic peptide L‐4F is a putative anti‐diabetic drug, has antioxidant and anti‐inflammatory proprieties and improves endothelial function. In obese mice L‐4F increases adiponectin levels, improving insulin sensitivity, and reducing visceral adiposity. We hypothesized that the pleiotropic actions of L‐4F can prevent heart and coronary dysfunction in a mouse model of genetically induced Type II diabetes. We treated db/db mice with either L‐4F or vehicle for 8 weeks. Trans‐thoracic echocardiography was performed; thereafter, isolated hearts were subjected to ischemia/reperfusion (IR). Glucose, insulin, adiponectin, and pro‐inflammatory cytokines (IL‐1β, TNF‐α, MCP‐1) were measured in plasma and HO‐1, pAMPK, peNOS, iNOS, adiponectin, and superoxide in cardiac tissue. In db/db mice L‐4F decreased accumulation of subcutaneous and total fat, and increased insulin sensitivity and adiponectin levels while lowering inflammatory cytokines ( P < 0.05). L‐4F normalized in vivo left ventricular (LV) function of db/db mice, increasing ( P < 0.05) fractional shortening and decreasing ( P < 0.05) LV dimensions. In I/R experiments, L‐4F prevented coronary microvascular resistance from increasing and LV function from deteriorating in the db/db mice. These changes were associated with increased cardiac expression of HO‐1, pAMPK, peNOS, and adiponectin and decreased levels of superoxide and iNOS ( P < 0.01). In the present study we showed that L‐4F prevented myocardial and coronary functional abnormalities in db/db mice. These effects were associated with stimulation of HO‐1 resulting in increased levels of anti‐inflammatory, anti‐oxidative, and vasodilatatory action through a mechanism involving increased levels of adiponectin, pAMPK, and peNOS. J. Cell. Biochem. 112: 2616–2626, 2011. © 2011 Wiley‐Liss, Inc.