Cases of liver abscess complicated by portal vein thrombosis are relatively rare. We report a case of liver abscess caused by α-hemolytic streptococci and complicated by portal vein thrombosis. A 51-year-old male presented with fever and right hypochondralgia. He had watery diarrhoea and bloody stool for over 1 month before presentation. Laboratory tests showed elevated hepatobiliary enzymes, inflammation findings, and anemia. Abdominal imaging revealed liver abscess in the right lobe and thrombosis of right and left branches of the portal vein; no thrombosis was observed in the extrahepatic portal vein. Colonoscopy revealed nonspecific colitis without diverticula or malignancies, and no possible causes of liver abscess except for enterocolitis were detected. Clinical course and laboratory findings indicated that an amoebic liver abscess was unlikely. Blood and pus cultures were positive for α-hemolytic streptococci. A diagnosis of liver abscess caused by α-hemolytic streptococci and complicated by portal vein thrombosis was made. The size of the liver abscess reduced, and inflammation findings resolved with 3 weeks of antibiotic treatment and abscess drainage. Portal vein thrombosis disappeared after 2 week anticoagulant therapy.