The rapid growth of smartphone adoption and use in the Middle East has led to some critical post-adoption issues, including ensuring that smartphones are used securely. Moreover, there is a gap in the existing literature on the perceptions and behaviour of individual consumers, especially millennials, in relation to mobile security and dealing with smartphone security threats. Little research on this subject has been carried out in developing countries, particularly in the Middle East, in a cross-national context. Therefore, this research aims to analyse the factors that can affect smartphone security behaviour among millennials in a cross-national context in the Middle East. The model developed in this research is based on a combination of the protection motivation theory (PMT) and the extended unified theory of acceptance and use of technology (UTAUT2), with additional factors specifically related to millennials’ smartphone security behaviour in the Middle East. The initial findings indicate that (1) there is a gap in research on the security behaviour of Arab millennials, despite the existence of serious security threats associated with their use of these technologies; and (2) there is a gap in research on similarities and differences in smartphone security behaviour among consumers in a cross-national context. A questionnaire will be distributed online to consumers who are 18–29 years old in Iraq, Jordan and the UAE. This is the first research to study millennial Arabs’ security behaviour around smartphones and mobile applications in a cross- national context. In addition, the conceptual framework proposed in this research combines the PMT and the UTAUT2, with a further extension via the inclusion of three additional factors: privacy concerns; security threats related to smartphone-specific characteristics; and cybersecurity acculturation. Furthermore, this research bridges the gap in knowledge in terms of addressing the lack of research on millennials smartphone users in the Middle East region as they form the largest segment of the population.