The present study found that serum H2S level, H2S production rate, CSE mRNA and CSE protein levels were increased in CVB3-induced myocarditis. dl-proparglygylcine (PAG), an irreversible CSE inhibitor, decreased the infected myocardium titers on postinfection day 4, while NaHS, a H2S donor, alleviated myocardial injury and necrosis, inflammatory cell infiltration and interstitial edema on postinfection day 10. These data reveal that the CSE/H2S pathway is upregulated in the heart in a murine model of CVB3-induced myocarditis and that inhibition of endogenous H2S is beneficial to treatment early in the disease while administration of exogenous H2S is protective to infected myocardium during the later stage.