Immunoglobulin G4 (IgG4)-associated autoimmune hepatitis (AIH) was recognized as a new disease entity; however, IgG4-associated de novo AIH after the liver transplantation had not been reported yet. Herein we have described a 56-year-old man who developed IgG4 de novo All as 1 year post liver transplantation after receiving pegylated interferon alpha-2a and ribavirin therapy for hepatitis C virus recurrence. The histopathologic evidence showed an aggressive lymphoplasmacytic interface hepatitis with centrilobular necrosis (plasma cells > 30%) and IgG4-positive plasma cells (>10 per high power field). Serum IgG (9220 mg/dL) and IgG4 (3289 mg/dL) were also elevated. Improvement of liver function tests (LFTs) by prednisone and azathioprine therapy are manifested as normalized alanine aminotransferase and IgG levels. IgG4 relates to more severe histological activity; however, it is believed to be a good prognostic predictor of a response to prednisone plus azathioprine therapy especially with early diagnosis and timely management.