As al-Walid grew older, Hisham became displeased with him and urged him to step aside in favour of Hisham's son. Hisham spoke to al-Walid about his drinking and dissolute life. The caliph commanded al-Walid to send away his best drinking companion. He also cut off funds to his heir and strongly encouraged him to be more respectful in religious matters.
Al-Walid succeeded to the throne on the death of Hisham on 6 February 743. As heir, al-Walid was known for his open-handedness. As caliph, he took special care of the crippled and blind, increasing their stipend. He named his two sons, al-Hakam and Uthman, to succeed him in that order as documented by a letter dated 21 May 743 in al-Tabari Tabari also quotes a number of al-Walid's poems.
Al-Walid at first confirmed Nasr ibn Sayyar as governor of Khurasan. However, bribed by Yusuf ibn Umar, the caliph dismissed him. Al-Walid appointed his uncle Yusuf ibn Muhammad governor of Medina. At the same time, Yahya ibn Zayd, the son of Zayd ibn Ali, was found in Khurasan. Nasr urged him to present himself to the caliph, to maintain Islamic unity. However, Yahya chose another path and after initial victory was slain.
Al-Walid put Sulayman ibn Hisham in prison. Such a deed, as well as his reputed drinking, singing and immorality aroused opposition. Al-Walid was fond of versifying and he arranged horse races. The upright Yazid ibn al-Walid spoke against the new ruler's moral laxity. A group began plotting his assassination. When approached, Khalid ibn Abdallah al-Qasri declined to join in and even cautioned al-Walid. However, his vague warning aroused al-Walid's ire. He imprisoned Khalid and then gave him to Yusuf ibn Umar for fifty million dirhams. Yusuf tortured and killed Khalid. This intensely angered many of al-Walid's own relatives.
Hearing of the plot, Marwan ibn Muhammad wrote from Armenia urging a more prudent course of action, one more promising for the stability of the state and the preservation of the Umayyad house. This was disregarded and many armed men moved into Damascus. The caliph was besieged in a castle outside the city. He fought well, but on April 16, 744, at Al-Aghdaf, in modern Jordan, he was defeated and killed by the forces of Sulayman ibn Hisham. He was succeeded by his cousin Yazid III.