This article explores the drivers of North Korea and Iran’s nuclear aspirations and behaviour by employing the theoretical prisms of ‘security dilemma’, ‘regional security complex’ (RSC) and ‘social constructivism’. It argues that ideational values and interests are shaping Iranian and North Korean nuclear aspirations and behaviour. Conversely, the absence of positive inter-subjective understanding of the US and its allies regarding Iran and North Korea is influencing their nuclear non-proliferation policy towards these states.