PURPOSE: Biliary atresia (BA) is characterized by progressive inflammation of the biliary system. This inflammation persists and causes liver fibrosis, although jaundice disappears after Kasai portoenterostomy (KP). We aimed to confirm whether the oral administration of eicosapentaenoic acid (EPA) suppresses liver fibrosis in postoperative patients with BA. METHODS: We reviewed patients who underwent laparoscopic KP (lapKP) between January 2014 and September 2017. From December 2016, 30 mg/kg/day of EPA was orally administered to patients who opted to take medicine (EPA group). Patients who did not receive EPA were assigned to the non-EPA group. Mac-2 binding protein sugar chain modified isomer (M2BPGi) and hyaluronic acid (HA) levels were compared between the two groups in patients showing disappearance of jaundice at 6 months after the first lapKP. RESULTS: Seventeen patients in the non-EPA group and 11 in the EPA group were enrolled. At 6 months after the first lapKP, 10 patients in the non-EPA group and six in the EPA group were without jaundice. M2BPGi and HA levels were significantly lower in the EPA group. CONCLUSIONS: Liver fibrosis was suppressed in patients without jaundice 6 months after lapKP, who were administered EPA. We believe that periductular inflammation was alleviated by EPA supplementation.