Purpose To identify whether arterial enhancement pattern at MRI could predict the prognosis after surgical resection of intrahepatic mass-forming cholangiocarcinoma (IMCC). Materials and Methods Patients who underwent curative hepatic resection and preoperative MRI for IMCC from November 2007 to September 2016 were retrospectively evaluated. MRI enhancement pattern was classified by two radiologists. Recurrence and death data were retrieved until September 31, 2017. Prognostic factor analysis was performed by using preoperative and postoperative clinical-pathologic factors, as well as imaging findings. Results Data in 134 patients (median age, 63.0 years; 87 men and 47 women) were evaluated; median tumor size was 4.5 cm. Arterial phase MRI showed diffuse hypoenhancement in 33 patients, peripheral rim enhancement in 81 patients, and diffuse hyperenhancement in 20 patients. The 5-year risk of death in patients with IMCC with diffuse hyperenhancement was lower than that of patients with diffuse hypoenhancement or peripheral rim enhancement (5-year risk of death: 5.9% vs 87.9% vs 59.2%). Diffuse hypoenhancement (hazard ratio [HR], 41; 95% confidence interval [CI]: 5, 312; P < .01) and peripheral rim enhancement (HR, 11; 95% CI: 2, 85; P = .02) were associated with an increased risk of death compared with diffuse hyperenhancement. Patients with diffuse hyperenhancement of IMCCs had more frequent chronic liver disease (13 of 20; 65%), less frequent vascular invasion (six of 20; 30%), and less frequent tumor necrosis (three of 20; 15%) than other enhancement group (P < .05 for all). Conclusion The MRI arterial enhancement pattern was a prognostic marker in the preoperative evaluation of patients with resectable intrahepatic mass-forming cholangiocarcinoma. © RSNA, 2019 Online supplemental material is available for this article. See also the editorial by Yoon and Lee .