Drawing on the construct of 'externalisation', this article examines how and why national policy experts use international knowledge in education policymaking. To understand how national policy experts deal with external source of information and expertise, I analysed the bibliographic references in policy documents prepared for an education reform and conducted network-cued interviews with local policy experts in the United States, South Korea, and Norway. The results revealed that national policy actors' utilisation of international knowledge varies across countries in terms of frequency, function, and level of engagement. The national differences suggest that each country has internalised the act of externalisation in the national policy process, reflecting its own policymaking and reform contexts.