Idiopathic hypereosinophilic syndrome (HES) is a rare, heterogeneous disorder characterized by a strikingly high eosinophil count (>1,500 cells/μL), over a long period of time (>6 months), with end organ damage. We present a 60-year-old patient with idiopathic HES with isolated liver involvement, a rare systemic disease and a rare solid organ involvement. The patient had a thorough investigational work up until HES was established, including liver biopsy. He needed intensive immunosuppressive treatment at first with steroids, then with azathioprine in conjunction with a low dose of steroids. After 16 years of follow-up, the patient showed no evidence of liver dysfunction. To the best of our knowledge, this is the longest follow-up for a patient with HES-associated chronic hepatitis. Our observation suggests that, with appropriate treatment, liver involvement in HES may be well controlled without deterioration to advanced liver failure.