The article offers a critique of International Relations (IR) theories of nationalism and foreign policy, supplemented by an analysis of the Nationalism Studies literature on the subject. Following a discussion of the ‘paradoxical status’ of nationalism in IR, the article outlines a more eclectic and non-paradigmatic approach – encapsulated in the concept of ‘nationalist beliefs’ – that emphasises the role of cognitive psychological variables to generate a more nuanced understanding of the relationship between nationalism and foreign policy and related outcomes. The article proposes a novel conceptualisation of nationalism to better understand foreign policy in the decade of New Nationalism.