Myocarditis is a clinically serious disease. Tea catechins have been shown to reduce inflammation; however the effects of catechins on the development of myocarditis have not been well studied. To clarify the role of catechins, using an experimental autoimmune myocarditis (EAM) model. Lewis rats were immunized with porcine cardiac myosin to establish EAM. Tea catechins were administered orally from day 0 to day 21 (Group A, n=12), from day 14 to day 21 (Group B, n=8), or saline (Group C, n=9) daily. Rats were killed on day 21. Echocardiograms indicated that Group A showed significantly improved cardiac function compared to Group C. Pathologically, non-treated EAM hearts showed severe myocardial cell infiltration and fibrosis; however Group A showed significantly less area. Immunohistochemistry revealed enhanced expression of NF-kappaB and ICAM-1 in non-treated EAM hearts, which was suppressed by catechin administration in Group A. mRNA levels of TNF-alpha were decreased and Th2 cytokines were markedly enhanced in Group A compared with the control group. Late catechin administration (Group B) showed limited effects on EAM. The catechins suppressed ventricular remodelling in EAM; thus catechin treatment might be a promising option for the prevention of EAM myocarditis.