Non-alcoholic fatty liver disease has been observed in over 30% of patients who have received tamoxifen therapy. However, tamoxifen-induced non-alcoholic steatohepatitis (NASH) cirrhosis has never been reported in Korea. A 41-year-old woman was diagnosed with invasive ductal carcinoma in the left breast. She had well-controlled type 2 diabetes mellitus, hypertension, and chronic hepatitis B. Ultrasonography showed mild fatty liver. Chronic hepatitis B had been treated with clevudine one month before the diagnosis of breast cancer. The patient was diagnosed with NASH cirrhosis 39 months after tamoxifen treatment. Careful observation for the development of NASH cirrhosis is warranted during tamoxifen therapy.