Born Abu Ali Hasan ibn Ali al-Tusi to a family tied to local administration in Khurasan. His upbringing in the eastern Iranian world exposed him early to Persian chancery practice and Sunni religious learning.

As a young man he studied Sunni jurisprudence, Arabic, and adab alongside the craft of official correspondence. This mix of scholarly prestige and administrative technique later made him invaluable at court.

After the Seljuks defeated the Ghaznavids at Dandanqan, Khurasan’s political landscape shifted rapidly. He began serving officials who were adapting Persian bureaucracy to new Turko-Seljuk rulers.

He worked within the household and offices associated with Chaghri Beg, helping manage revenue and petitions. His reputation grew as he balanced Turkic military elites with Persian scribal norms.

With Alp Arslan’s consolidation of power, Hasan al-Tusi became known for organizing provincial governance and stabilizing finances. He built networks among judges, tax officials, and commanders across Khurasan.

Alp Arslan appointed him chief vizier, granting authority over the divans and the imperial chancery. He coordinated campaigns with policy, ensuring provisioning, pay, and provincial compliance during expansion.

As Alp Arslan pushed into Armenia and Georgia, Nizam al-Mulk oversaw logistics, taxation, and new appointments. He aimed to turn conquest into durable rule by integrating local elites and revenues.

The Seljuk victory over Byzantium at Manzikert opened Anatolia to Turkic settlement and new frontier politics. Nizam al-Mulk worked to keep the state’s fiscal base steady while rewarding commanders and tribes.

After Alp Arslan’s death, he supported Malik-Shah I and helped navigate rival claims within the ruling house. His authority in the bureaucracy made the transition smoother and preserved imperial cohesion.

He sponsored the Nizamiyya institutions to promote Sunni scholarship and train judges and administrators loyal to the Seljuk order. These schools strengthened the influence of scholars like al-Juwayni and later al-Ghazali.

He refined the use of iqta land-revenue assignments to pay troops without collapsing the treasury. By enforcing records and inspections, he tried to curb abuses by amirs and protect peasant cultivation.

Court politics hardened as Turkan Khatun promoted her allies and sought influence over succession planning. Nizam al-Mulk defended bureaucratic authority and Malik-Shah’s central control against competing households.

As Hasan-i Sabbah established Nizari power at Alamut, targeted violence and propaganda unsettled Seljuk officials. Nizam al-Mulk supported security measures and intelligence efforts to protect governors and judges.

He used patronage and appointments to align Abbasid caliphal prestige with Seljuk military power. The Nizamiyya of Baghdad became a centerpiece for Sunni legal training and public sermons in the capital.

He composed the Siyasatnama, blending administrative experience with moral lessons, anecdotes, and concrete rules for ruling. Addressed to Malik-Shah’s circle, it emphasized justice, surveillance of officials, and stable taxation.

He was killed near Nahavand by an assailant often linked in later sources to the Nizari Isma'ilis. His death removed the empire’s chief administrator just before Malik-Shah’s own death triggered succession crisis.