The paper will focus on explaining the nature, extent and evolution of terrorism through the role of Chemical, Biological, Radiological and nuclear weapons (CBRN) such as Bio-Chemical Weapons (BCWs). It will further discuss the role of religious terrorist organizations, such as Al Qaeda and ISIS/Deash in re-defining terrorism in contemporary era by acquiring BCWs. Moreover, it will underscore the lethality and level of threat posed by BCW’s when employed by the non-state actors. Additionally, it will highlight various motivating factors including political, religious, and psychological which can act as a driving force for the terrorists and non-state actors to use BCWs. Lastly, it will suggest that a change in the means and methods of terrorism predominantly comprising of BCWs as a weapon of choice for the terrorists is on the cards and it is likely remaining the feature of international politics in the days and years to come if the international treaty regime on BCWS does not adequately address the phenomenon of non-state actors. Keywords: Terrorist Organizations, Bio-Chemical Weapons, Al Qaeda, Islamic State, Rational Actors, Biological and Toxin Weapons Convention, Chemical Weapon Convention, CBRN.