Lenalidomide is a potent immunomodulatory agent capable of downregulating proinflammatory cytokines such as tumor necrosis factor-α (TNF-α) and upregulating anti-inflammatory cytokines. Lenalidomide has been shown to elicit cardiovascular effects, although its impact on cardiac function remains obscure. This study was designed to examine the effect of lenalidomide on cardiac contractile function in ob/ob obese mice. C57BL lean and ob/ob obese mice were given lenalidomide (50 mg/kg/day, p.o.) for 3 days. Body fat composition was assessed by dual-energy X-ray absorptiometry. Cardiomyocyte contractile and intracellular Ca2+ properties were evaluated. Expression of TNF-α, interleukin-6 (IL-6), Fas, Fas ligand (FasL), the short-chain fatty acid receptor GPR41, the NFκB regulator IκB, endoplasmic reticulum (ER) stress, the apoptotic protein markers Bax, Bcl-2, caspase-8, tBid, cytosolic cytochrome C, and caspase-12; and the stress signaling molecules p38 and extracellular signal-regulated kinase (ERK) were evaluated by western blot. ob/ob mice displayed elevated serum TNF-α and IL-6 levels, fat composition and glucose intolerance, the effects of which except glucose intolerance and fat composition were attenuated by lenalidomide. Cardiomyocytes from ob/ob mice exhibited depressed peak shortening (PS) and maximal velocity of shortening/relengthening, prolonged time-to-PS and time-to-90% relengthening as well as intracellular Ca2+ mishandling, which were ablated by lenalidomide. Western blot analysis revealed elevated levels of TNF-α, IL-6, Fas, Bip, Bax, caspase-8, tBid, cleaved caspase-3 caspase-12, cytochrome C, phosphorylation of p38, and ERK in ob/ob mouse hearts, the effects of which with the exception of Bip, Bax, and caspase-12 were alleviated by lenalidomide. Taken together, these data suggest that lenalidomide is protective against obesity-induced cardiomyopathy possibly through antagonism of cytokine/Fas-induced activation of stress signaling and apoptosis.