The combination therapy of pegylated interferon and ribavirin is the mainstay of treatment for chronic hepatitis C patients. Anti-viral therapy is commonly associated with side effects such as headache, fever, myalgia, and arthralgia. However, anti-viral therapy can continue because these side effects are mostly mild and can be improved with supportive management. Anti-viral therapy should be stopped promptly if serious side effects, such as interstitial pneumonitis or hemolytic anemia occur, although those serious side effects are rare. There were a few case reports of interferon-related interstitial pneumonitis worldwide. In Korea, one atypical case report of interstitial pneumonitis has been reported, which followed the combination therapy of interferon-alpha and ribavirin in a patient with chronic hepatitis C. We present a case of interstitial pneumonitis and pancytopenia following the combination therapy of pegylated interferon and ribavirin in a patient with chronic hepatitis C.