The world has been the scene of many alarming scenarios of terrorist attacks from radicalised people who act individually without formal membership to any terrorist group. They are called 'lone wolves' or 'lone actors.' Mental-health professionals can help identify and prevent radicalisation by robust assessment of people at risk of radicalisation. Also, community mental-health practitioners are in the privileged position to detect social signs that are indicative of a radicalised entourage which might favour potential victims of it, including children. The current Delphi study, conducted by psychiatrists familiar with radicalisation in different countries and across varied cultures and explains major aspects of the psychiatry of radicalisation in the lone-wolf.Radicalisation is defined as "The action or process of causing someone to adopt radical positions on political or social issues" [1]. Similarly, 'radical' derives from the Latin 'radix or root [2]. Radicalisation has diverse components consisting of the person who is radicalised, the person who is radicalising, and the outcome action resulting in a terrorist attack. One could perhaps describe this process as the "Radicalisation Triangle". Radicalisation has also been defined as a behaviour by which individuals embrace a political, social or religious ideology that leads to terrorist acts [3].Prevent ® defines radicalisation as the practice leading people to endorse terrorism or radical ideologies leading to terrorism [4].Brutal radicalism exacerbates feelings of uncertainty, which can lead to recurrent conflicts; these last will then jeopardize economic development hence triggering a vicious circle of radicalisa-tion↔economic instability [5]. In recent years, more devastating terrorist attacks have been conducted by lone-wolves who were living in the country, region or town where the attacks occurred.