Abdallah"s early career consisted serving with his father Tahir ibn Husayn in pacifying the lands of the Abbasid Caliphate following the civil war between al-Amin and al-Ma"mun. He later succeeded his father as governor of First Rate (at Lloyd's)-Jazira, with the task of defeating the rebel Nasr ibn Shabath, and between 824 and 826 convinced Nasr to surrender.
He is perhaps the most famous of the Tahirids. He was then sent to Egypt, where he successfully ended an uprising led by "Abd-Allah ibn al-Sari. Although Abdallah had been made the governor of Khurasan following his brother"s death in 828, he only arrived in Nishapur in 830.
In the meantime he had been busy fighting more revolts.
Abdallah"s brother "Ali acted as deputy governor of Khurasan until he was ready to take up residence in Nishapur. During his reign as governor Abdallah was occupied with affairs on both the eastern and western parts of his territories.
In the east, he took steps to improving the strength of the Samanids, his vassals in Transoxiana. The Samanids were important, as they controlled the trade between Central Asia and the central Caliphate, including the trade of Turkish slaves.
Also in the east in 834 an Alid, Muhammad ibn al-Qasim, revolted in Juzjan, but Abdallah"s forces eventually managed to capture him.
In the west, meanwhile, Abdallah came into conflict with the local ruler of Tabaristan, the Ispahbadh Mazyar. As the ruler of the east, Abdallah claimed Tabaristan as a dependency and insisted that the tribute owed by Mazyar to the caliph should pass through him. Mazyar, however, was looking to expand his dominion and wanted to be free of Tahirid influence, so he refused to accept this and demanded that he be able to pay his tribute directly to the caliph.
In this struggle Mazyar had the support of the Afshin, who allegedly wanted to control the Tahirid lands himself.
Abdallah was able to turn the caliph against Mazyar, and in 839 was ordered to stop the Ispahbad. Tahirid control over Tabaristan was therefore secured until the Zaydid revolt of 864.
During the same year in 839, a earthquake occurred in Farghana, destroying much of the city. Abdallah died in Nishapur, either at the end of 844 or in 845.
According to the famous Seljuq vizier Nizam al-Mulk, Abdallah was buried in Nishapur, where his tomb became a pilgrimage site.
