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. The nuclear ambitions and diplomacy of North Korea and Iran could be better understood by looking at the role of ideational, security and structuralism models that are influencing their threat perception in the respective security complexes. Thus, addressing the ideational factors and security dilemmas of the two states can help in resolving the twin threats to nuclear non-proliferation in the 21st century.