When he was 13 years old Al-Mu'tamid's father made bestowed the title of Emir and appointed the Andalusi Arabic poet Ibn Ammar as his vizier. However, Al-Mu'tamid fell strongly under the influence of Ibn Ammar; and possibly in love. After one night of poetry and wine it was reported that Al-Mu'tamid insist they sleep together "on this same pillow." Al-Mu'tamid's father disapproved of the relationship and the influence of the vizier (not least because Ibn Ammar was a commoner) and sent him into exile in order to separate the two.
After the death of his father Abbad II al-Mu'tadid in 1069, he inherited Seville as caliph. One of his first acts was to recall Ibn Ammar and to bestow high political and military favours on him, including as Governor of Silves and Prime Minister of the government in Seville. Some sources suggest a lovers' quarrel after Ibn Ammar dreamt that Al-Mu'tamid was going to kill him. The caliph reassuring him that he would never do such a thing.
More likely the cause of resentment grew from the fact that the Prime Minister had let al-Mu'tamid's son, Prince al-Rasid, be captured and held hostage during a military campaign. He had also declared himself king of Murcia without properly acknowledging the rights of his own sovereign. The two men exchanged verses full of bitter criticisms and accusations. Murcia was subsequently lost and Ibn Ammar himself taken hostage. A final attempt to conspire with the young prince against his father proved too much for al-Mu'tamid who “fell into a rage and hacked him to death with his own hands”. After Ibn Ammar's death, the caliph was reported to have grieved bitterly and gave his former friend a sumptuous funeral.
Large parts of al-Andalus were under the dominion of al-Mu'tamid: to the west his dominion encompassed the land between lower Guadalquivir and Guadiana; plus the areas around Niebla, Huelva and Saltes. In the south it extended to Morón, Arcos, Ronda, and also Algeciras and Tarifa. The capital, Córdoba, was taken in 1070, lost in 1075, and regained in 1078.
Nevertheless, the family was still subject to taxation by the King of Castile, to whom they were vassals. The drain of these taxes effectively weakened the kingdom's power: al-Mu'tamid's decision to stop paying these taxes caused King Alfonso VI of Castile (who had already conquered Toledo in 1085) to besiege Seville. Al-Mu'tamid asked help from the Almoravids of Morocco against the Castilian king. Al-Mu'tamid supported the Almoravid ruler Yusuf ibn Tashfin against Alfonso in the Battle of Sagrajas in 1086. The Moroccans established themselves at Algeciras and, after defeating the Christians, occupied all the Islamic taifas, including in 1091 Seville itself. After they ravaged the city, al-Mu'tamid ordered his sons to give up the royal fortress (early Alcazar of Seville) in order to save their lives. When his son, Rashid, had advised him not to call on Yusuf ibn Tashfin, Al-Mu'tamid had rebuffed him:
I have no desire to be branded by my descendants as the man who delivered al-Andalus as prey to the infidels. I am loath to have my name cursed in every Muslim pulpit. And, for my part, I would rather be a camel-driver in Africa than a swineherd in Castile.
In 1091 Al-Mutamid was taken into captivity by the Almoravids and exiled to Aghmat, Morocco where he died (or was perhaps assassinated) in 1095. His grave is located in the outskirts of Aghmat.
He is also considered, in his own right, one of the greatest of the Andalusian poets. He was the father (or according other weaker sources the father-in-law, through his son, Fath al-Mamun death in 1091) of Zaida, mistress, and possibly wife, of Alfonso VI of Castile.