Feline coronaviruses (FCoVs) are the causative agents of severe systemic disease (feline infectious peritonitis: FIP) in domestic and wild cats. FCoVs have been classified into serotypes I and II. Type I FCoV is the dominant serotype (approximately 70-90%) worldwide. Therefore, it is necessary to provide antiviral agents for type I FCoV infection. In this study, we demonstrated that itraconazole (ICZ), practically used for fungal infections in cats, inhibits the type I FCoV infection. ICZ also exhibited antiviral effect in cells after viral infection, suggesting that ICZ could potentially be used as a therapeutic.