Internationalisation of the curriculum (IoC) as an important element of internationalisation has seen many challenges. The literature shows that successful IoC cases are rare. Drawing on the concepts of powerful knowledge and 'knowing', we argue that a more comprehensive understanding of knowledge engagement in the IoC process is needed. Currently, engaging knowledge appears to be a barrier to IoC, particularly in hard disciplines such as science and engineering. This study investigated how faculty members from different disciplines engaged knowledge in their approaches to IoC through semi-structured interviews with 34 faculty members based in three Hong Kong universities. The findings show that engaging knowledge is indispensable to IoC because it provides theoretical foundations for 'being' and substantiates discussions on global issues using disciplinary lenses. Furthermore, faculty members from all disciplines show productive ways of engaging knowledge, whilst the differences lie in the expected role of 'knower' and the relationship between 'knowing' and 'being'. Specifically, facilitating an intimate relationship between 'knowing' and 'being' through students' own dispositions was featured in soft disciplines, whilst taking perspectives based on scientific principles was identified in hard disciplines.