Global terrorism has become a major threat in the 21st century, thereby becoming the most prominent issue on the agenda of international relations. This study discusses the characteristics of global terrorism and the potential causes; why terror has become an international in the modern world. Although there are numerous sources about terrorism itself or international terrorism, few of them put sufficient arguments about the transformation process of terrorism from domestic level to the to the global level. First, what international terrorism initially reminds us is argued by making some comparisons between domestic and international terrorism. Than, briefly, the definition and its dilemma is noted. Subsequently, the historical perspective and the prevailing causes of internationalization or terror are examined more substantially. And the article ends with some concluding remarks relating the whole argument.