Biosecurity restrictions regulate the types of materials that international travellers can bring into certain countries. Australia is well known in international travel cultures for stringent customs regulations and checks on all incoming passengers. This blanket approach to biosecurity governance implies that all materials, even banal personal possessions or luggage, pose a potential threat to the nation’s biosecurity. This article explores how individuals prepare for and experience declaring personal belongings while migrating to and entering Australia. Drawing from interviews with recently arrived migrants on temporary visas, analysis of the required customs declaration card and government information, I highlight the inconsistencies of how materials, and the people who carry them, come under close scrutiny at the border. The findings show that the stringent surveillance of biosecurity perpetuates perceived risks and threats, relying on stereotypes of certain migrant and traveller profiles in the way biosecurity is promoted, monitored and enforced. Biosecurity manifests social, spatial, and material concerns in how it is performed and regulated, thereby transforming passive materials in a person’s luggage into active threats to national security, further complicating the rigid governance of international mobility and migration.