Like his father al-Musta‘lī (1094–1101), al-Amīr was controlled by the regent al-Afdal Shahanshah (1094–1121) and had little influence in political matters. However, after the overthrow of al-Afdal in 1121 he managed to gain control of government. His reign was marred by the loss of Tyre to the Crusaders, as well as by the continuation of the Ismā‘ilī Shī‘ah schism between the Nizārī and the Musta‘liyyah. This conflict climaxed in the assassination of al-Amīr on October 7 1130.
The lack of a direct heir to the Caliphate led to further power struggles, through which Al-Hafiz, a cousin of al-Amīr, eventually came to power.
The Musta‘liyyah claim that Taiyab abi al-Qasim was al-Amīr's rightful successor as Imām.