The cardioprotective effects of adiponectin (APN) against myocardial ischemia/reperfusion (MI/R) injury are well known. However, comprehension of the mechanisms mediating intracellular APN signaling remains incomplete. We recently demonstrate the antioxidant/antinitrative effects of APN are not dependent upon AMPK. Protein Kinase A (PKA) has been previously shown to be activated by APN, with uncertain relevance to APN cardiac protection. The current study determined whether the anti-oxidative/anti-nitrative effect of APN is mediated by PKA. Administration of APN (2 µg/g) 10 minutes before reperfusion significantly enhanced cardiac PKA activity, reduced oxidative stress and decreased infarct size. Knockdown of cardiac PKA expression (PKA-KD) by intramyocardial injection of PKA-siRNAs (>70% suppression) significantly inhibited APN cardioprotection determined by cardiac apoptosis, infarct size, and cardiac function. Moreover, PKA-KD virtually abolished the suppressive effect of APN on MI/R induced NADPH oxidase overexpression and superoxide overproduction, and partially inhibited the effect of APN on nitrative protein modification in MI/R heart. Mechanistically, APN significantly inhibited MI/R-induced IKK/IB phosphorylation and NFB activation, which were blocked in PKA-KD heart. Finally, the PKA-mediated antioxidant/antinitrative and cardioprotective effects of APN are intact in AMPK deficiency mice, suggesting that there is no cross-talk between AMPK and PKA signaling in APN cardioprotection. Collectively, we demonstrate for the first time that APN inhibits oxidative/nitrative stress during MI/R via PKA-dependent NFB inhibition.