Serological tumor markers are useful for detection of malignancies and evaluation of disease progression. However, some markers are rarely elevated in patients with benign diseases and without malignancies. We herein present a case of a liver abscess with a highly elevated carbohydrate antigen (CA 19-9) level in both the serum and abscess fluid. The serological level of CA 19-9 decreased with treatment. Although CA 19-9 is known to be a specific tumor marker, high serum levels of CA 19-9 can be observed in patients with pyogenic liver abscesses. CA 19-9 may also be a marker for treatment response in patients with liver abscesses.