Born as an Abbasid prince outside the main line of succession, al-Qadir received a good education, including in the tenets of the Shafi'i school of Islamic jurisprudence.

He denounced the Fatimids in the Baghdad Manifesto of 1011, and issued proclamations that for the first time codified Sunni doctrine in the so-called 'Qadiri Creed', taking the side of the traditionalist Hanbali school against the rationalist Mu'tazilites.

[6] Even the Buyid emir Fakhr al-Dawla, who ruled large parts of central and northern Iran until his death in 997, refused to recognize al-Qadir, continuing to mint coins in al-Ta'i's name.

[15] The only independent actions taken during the first decade of his caliphate were the completion in 993/4 of a Friday mosque in the Harbiyya quarter of Baghdad, begun by his uncle al-Muti' (r. 946–974),[6][16] and the public proclamation of his son Muhammad, then just eight or nine years old, as heir apparent, with the title of al-Ghalib Bi'llah, in 1001.

About 998, a certain Abdallah ibn Ja'far, a close relative of the deposed al-Ta'i, pretended to be the escaped caliph in Gilan and even gained the backing of the local ruler for a time, before he was discovered.

[10] At about the same time, in Transoxiana, another distant cousin, Abdallah ibn Uthman, a descendant of the 9th-century caliph al-Wathiq, pretended to be al-Qadir's designated heir and won the support of the local Karakhanid ruler.

[19] Ambitious to subdue the Buyid emirates to the east under his own rule, Baha al-Dawla forced al-Qadir to finance the military preparations to that effect, which progressively emptied the caliphal coffers.

[6] The Buyid emirs that followed Baha al-Dawla were also increasingly engaged in an unrestrained competition for supremacy amongst themselves, in which control of Baghdad and of the caliph, who could dispense titles and tokens of legitimacy, was of central importance.

[25] This in turn gave al-Qadir greater freedom of action,[20][26] and placed him on much better and more equal footing with Baha al-Dawla's successors, who were careful to maintain good relations with the caliph.

[35] Mahmud's lavish gifts also helped alleviate somewhat the poverty of the caliph as a result of Buyid exactions; nevertheless, at his death, al-Qadir left an empty treasury.

[16] Although al-Qadir held no temporal political power, he nevertheless managed to exploit the opportunities he was presented with to greatly restore the moral and religious authority of the caliphate.

[32] In this, he made good use of his own education in Islamic jurisprudence (fiqh), which gave him an authority to speak as a member of the emerging class of religious scholars (ʿulamāʾ).

[6] In 1006, a violent controversy broke out over a recension (muṣḥaf) of the Quran claimed to have belonged to Ibn Mas'ud, which was espoused by Shi'a scholars against the canonical version, but firmly rejected by the Sunnis.

Al-Qadir responded by sending an embassy to Baha al-Dawla that succeeded in getting the Buyid ruler to apply pressure on the Uqaylid emir, who soon returned to Abbasid allegiance.

[6][20] The Emirs of Mecca also recognized Fatimid suzerainty, and for many years, Hajj pilgrims from Iraq were unable to visit the city as the security of their passage could not be guaranteed.

[6][20] Singling out the Fatimids as the first target of his active involvement in public affairs was a clever move, as the Buyids not only tolerated it but regarded it as useful for their own purposes, and an attack on the rival Shi'a sect gathered support even from Twelver notables.

[48] Mu'tazilism had in the past been supported by Abbasid caliphs, most notably al-Ma'mun (r. 813–833), who even instituted the Inquisition-like mihna to persecute the traditionalists who refused to accept the Mu'tazilite doctrine of Quranic createdness.

[49] In the event, the persecution not only failed, but backfired: the mihna was suspended, and the traditionalist Hanbali school emerged with its prestige strengthened and its doctrines more influential than before.

[6][51] Shortly after, on 27 January 1019,[52] inspired by Hanbali ideas, the caliph issued a decree, the Risāla al-Qādiriyya ('Epistle of al-Qadir'), which for the first time explicitly formulated Sunni doctrine.

[56] As al-Ghalib had died in January 1019,[57] in 1030 al-Qadir named his younger son Abu Ja'far, the future al-Qa'im, as his heir, a decision also taken completely independently of the Buyid rulers.

One of the most notable Sunni scholars, Ahmad ibn Hanbal, founder of the Hanbali school, had been persecuted by the Inquisition-like miḥna, founded by Caliph al-Ma'mun (r. 813–833).

Al-Mawardi's al-Iqna or even his famous al-Ahkam al-Sultaniyya, the Mukhtasars of al-Quduri and Abd al-Wahhab al-Maliki, as well as a refutation of bāṭinī doctrines by Ali ibn Sa'id al-Istakhri, are said to have been composed on his request.

[64] Al-Qadir's edicts do not survive in full in the sources, but a consolidated 'Qadiri Creed' (al-Iʿtiqād al-Qādirī), that has come down to the present day, was current by the reign of al-Qa'im.

[53] Al-Qadir's statement of faith provided a definition of belief, and, conversely, of unbelief;[66] giving Sunni jurists a template by which to issue rulings (fatwā).

[32] Al-Qadir thus laid the ideological foundations for what has been termed the 'Sunni Revival' of the 11th century, which culminated with the destruction of the Buyids by the Seljuk Turks, a new steppe power who saw themselves as champions of Sunnism and of the Abbasid caliph.