Background-: Inflammation plays a critical role in adverse cardiac remodeling and heart failure. Therefore, approaches geared toward inhibiting inflammation may provide therapeutic benefits. We tested the hypotheses that genetic deletion of interleukin-10 (IL-10), a potent antiinflammatory cytokine, exacerbates pressure overload-induced adverse cardiac remodeling and hypertrophy and that IL-10 therapy inhibits this pathology. Methods and Results-: Cardiac hypertrophy was induced in wild-type and IL-10 knockout mice by isoproterenol (ISO) infusion. ISO-induced left ventricular dysfunction and hypertrophic remodeling, including fibrosis and fetal gene expression, were further exaggerated in knockout mice compared with wild-type mice. Systemic recombinant mouse IL-10 administration markedly improved left ventricular function and not only inhibited but also reversed ISO-induced cardiac remodeling. Intriguingly, a very similar cardioprotective response of IL-10 was found in transverse aortic constriction-induced hypertrophy and heart failure models. In neonatal rat ventricular myocytes and H9c2 myoblasts, ISO activated nuclear factor-κB and inhibited signal transducers and activators of transcription 3 (STAT3) phosphorylation. Interestingly, IL-10 suppressed ISO-induced nuclear factor-κB activation and attenuated STAT3 inhibition. Moreover, pharmacological and genetic inhibition of STAT3 reversed the protective effects of IL-10, whereas ectopic expression of constitutively active STAT3 mimicked the IL-10 responses on the ISO effects, confirming that the IL-10-mediated inhibition of nuclear factor-κB is STAT3 dependent. Conclusion-: Taken together, our results suggest IL-10 treatment as a potential therapeutic approach to limit the progression of pressure overload-induced adverse cardiac remodeling. © 2012 American Heart Association, Inc.