'Abd al-Mu'min succeeded Ibn Tümart after the Almohad defeat at al-Buhayra and the Mahdī's death in 524/1130. His accession in 527/1133 was not universally accepted, and the movement's internal tensions were intensified by questions of tribal representation and succession. The account presents his rise as more than a local messianic succession, linking it to his own position within the movement and to a broader political project.

During a reign described as lasting thirty years, 'Abd al-Mu'min was portrayed as a capable general, energetic leader, and statesman. His immediate challenge was to wage jihad against the Almoravids while organizing and consolidating a heterogeneous Almohad coalition. He pursued these aims through a deliberate strategy that combined military operations with economic objectives.

'Abd al-Mu'min avoided an immediate confrontation on the Moroccan plains and instead moved through the Atlas, Sus, Wādī Dar'a, the Middle Atlas, Tafilalt, and the Djebala. These campaigns secured mountain routes, mineral resources, and access to the commercial connections between sub-Saharan Africa and the Mediterranean. Once the Almoravid position had been encircled, he launched the offensive into the plains.

His victories extended from Morocco into the central Maghrib. The Almohads took Tlemcen, Algiers, Bijāya, the Kal'a, and Constantine, while the defeat of the Arab coalition at Setif in 1153 strengthened his authority. He nevertheless faced revolts among Almohads and conquered populations, and he responded with severe repression and political reorganization.

After suppressing opposition from members of Ibn Tümart's family and other Almohad factions, 'Abd al-Mu'min prepared a dynastic succession. At Salé in 1156–7, he obtained recognition for Muhammad as heir presumptive and appointed his other sons as governors of major cities with the title of sayyid. This step marked the movement's transition from charismatic leadership toward hereditary imperial government.