We report a case of a solitary liver abscess in a 5-week-old female. She was full term, and there were no predisposing events or immune deficiencies. The only sign of her disease was a gradually distended abdomen. A prior episode of fever with possible occult bacteremia was implicated in the development of her abscess. The abdominal sonography and magnetic resonance image (MRI) did not provide any definite preoperative diagnostic information. Surgical resection of the abscess and a short course of antibiotic therapy cured the disease. This patient was still well following 2 years of check-ups by sonography. The possibility of a pyogenic liver abscess should be considered in the differential diagnosis of neonatal hepatic mass. That is, even if there is not a definite diagnostic focus on finding an infection.