Due to the complex pathophysiology and serious outcomes of autoimmune myocarditis, we sought to determine whether ethanolic lemon balm extract (LBE) could attenuate disease progression and development of dilative cardiomyopathy (DCM). EAM was induced in Dark Agouti rats by immunization with porcine myosin. Fifty animals were allocated to five groups: healthy controls, untreated EAM, and EAM treated with LBE (50, 100, or 200 mg/kg) for six weeks. Hemodynamic parameters were monitored, and echocardiography assessed cardiac structure and function. Inflammatory, oxidative, fibrotic, and apoptotic markers were analyzed. Immunological profiling revealed that LBE significantly decreased proinflammatory cytokines (IL-1, IL-6, TNF-α, IL-4, IL-17) while restoring anti-inflammatory IL-10 levels (p < 0.05). Antioxidant activity was confirmed by reduced levels of O2-, H2O2, and TBARS, accompanied by significant increases in SOD, CAT, and GSH activity (p < 0.05), and upregulation of SOD1 and SOD2 gene expression. Additionally, LBE (200 mg/kg) markedly reversed fibrotic remodeling through suppression of TGF-β expression and collagen deposition, as shown by Sirius Red staining, and mitigated apoptosis by modulating Bax/Bcl-2 balance and reducing TUNEL-positive cells. Collectively, these findings suggest that LBE exerts strong cardioprotective effects in EAM by regulating inflammatory, oxidative, fibrotic, and apoptotic pathways, thereby preventing myocarditis progression toward DCM.