[6] The founder of the Tahirid dynasty was Tahir ibn Husayn, a Sunni Persian of dehqan origin,[8][9] who had played a major military role in the civil war between the rival caliphs al-Amin and al-Ma'mun.

Oppressive policies in Tabaristan, another dependency of Khorasan, resulted in the people of that province revolting and declaring their allegiance to the independent Zaydi ruler Hasan ibn Zayd in 864.

Besides their hold over Khorasan, the Tahirids also served as the military governors (ashab al-shurta) of Baghdad, beginning with Tahir's appointment to that position in 820.

After he left for Khorasan, the governorship of Baghdad was given to a member of a collateral branch of the family, Ishaq ibn Ibrahim, who controlled the city for over twenty-five years.

The following year, he forced al-Musta'in to abdicate and recognized al-Mu'tazz as caliph, and in exchange was allowed to retain his control over Baghdad.

[22] Violent riots plagued Baghdad during the last years of Abdallah's life, and conditions in the city remained tumultuous after he died and was succeeded by his brothers, first Ubaydallah and then Sulayman.

In 891, however, Badr al-Mu'tadidi was put in charge of the security of Baghdad in place of the Tahirids,[19] and the family soon lost their prominence within the caliphate after that.

Iranians were adapting Arab-Islamic cultural tenets through a process of 'take the best, leave the rest'.Within this context, Mahendrarajah adds that the Tahirids were specifically responsible for initiating the process by which Persian became written in the Perso-Arabic script, referring to this as "an ingenious Iranian adaption that allowed them to retain the heritage and charm of the Persian language".