This paper derives from the ongoing “Nativism, Islamophobism and Islamism in the Age of Populism: Culturalisation and Religionisation of what is Social, Economic and Political in Europe” project conducted under the supervision of the Principle Investigator, Prof. Dr. Ayhan Kaya, and funded by the European Research Council with the Agreement Number 785934. The purpose of this article is to investigate the psychology’s foundational theories and seek how they have (or might have) contributed to the study of radicalisation from psychological perspective. Radicalisation theories are diverse, though not necessarily antagonistic to each other. Rather, each model addresses a somewhat different aspect of radicalisation, or depicts it from a distinctive disciplinary perspective at a different level of analysis. Psychology – the study of individuals’ beliefs, thoughts, emotions and behaviour, may be uniquely positioned to assess and inform theories of radicalisation. This paper selected four psychological schools of thought – Psychoanalytic, Cognitive, Behaviourist and Socio-Cultural – to assess and inform theories of radicalisation. These four psychological approaches focus on different aspects of human psyche and study processes of change differently. Taken independently, each offers a valuable conceptualization of radicalisation experience. Taken together, however, certain commonalities emerge. These commonalities indicate factors that are deemed important contributors to radicalisation.