Overlap syndrome between primary sclerosing cholangitis (PSC) and autoimmune hepatitis (AIH) is extremely rare in Japan. We herein report two adult patients with PSC-AIH overlap syndrome. They were diagnosed with PSC-AIH overlap syndrome based on the findings of endoscopic retrograde cholangiography and liver biopsy, and using the International Autoimmune Hepatitis Group scoring system. In both cases, PSC preceded AIH, and combination therapy with steroid and ursodeoxycholic acid was effective. Because there are few reported cases in Japan, it is important to study more cases to shed light on the clinical and pathological features of PSC-AIH overlap syndrome.