The Fatimid adopted the Ismaili Doctrine as an official sect of the state. But this decision wasnt gone smoothly as many think. Although the Ismaili history was kept in shadow for a long time, the modern researches proved that the dissentions were a dominant aspect from the very beginning.The aim of this research is to shed light on those dissentions and its effects on the Fatimids. The research is divided into three sections: section one deals with the main reasons behind the dissensions, especially the doctrines one. Section two handles those sects that emerged as a result of the dissentions. The third section focuses on the main effects of the Ismaili sectarian struggle .