Theophylline, a bronchodilator, induces cardiotoxicity due to its narrow therapeutic index. Lipid emulsion is used as a nonspecific antidote. However, its effects on theophylline-induced cardiotoxicity remain unknown. This study aimed to examine the effects of lipid emulsion on cardiotoxicity induced by toxic doses of theophylline in H9c2 rat cardiomyoblasts. The effects of theophylline and lipid emulsion (Lipofundin MCT/LCT), alone or in combination, on cell viability and migration were examined. Moreover, their effects on cleaved caspase-3, Bax/Bcl-XL ratio, and cleaved caspase-9 and caspase-8 expression, nuclear factor-κβ (NF-κβ) phosphorylation, and TUNEL-positive cells were examined. Theophylline treatment decreased cell viability. Lipofundin MCT/LCT (0.1-1%) with 50% longchain and 50% medium-chain fatty acids inhibited the theophylline-induced reduction in cell viability (3×10-3 M). It partially inhibited the theophylline-induced decrease in cell migration. Further, it reversed the theophylline-induced increase in cleaved caspase-3, Bax/Bcl-XL ratio, and cleaved caspase-9 expression as well as NF-κβ (Ser536) phosphorylation. However, theophylline treatment did not alter cleaved caspase-8 expression. Additionally, lipid emulsion inhibited theophylline-induced increase in TUNELpositive cells. Taken together, these results suggest that lipid emulsion reverses theophylline-induced apoptosis in cardiomyoblasts via inhibition of the mitochondrial apoptotic pathway associated with NF-κβ (Ser536) phosphorylation, indicating its potential for treating theophylline-induced cardiotoxicity.