He was raised in Fars along with his brother Malik-Shah III. In 1148, their uncle Sultan Ghiyath ad-Din Mas'ud, who had no heirs and was in a weak position, appointed Malik-Shah III as heir, and gave his daughter in marriage to him. On 13 September 1152, Mas'ud died at Hamadan, and Malik-Shah III ascended the throne. In 1153, Muhammad, who was then in Khuzestan, marched towards Iraq and deposed his brother Malik-Shah III from the Seljuq throne, and ascended the throne himself. Meanwhile, the insurgent Abbasids under caliphal-Muqtafi was seizing the Turks of Iraq, and in 1155 supported a rival claimant to the throne, Suleiman-Shah. Furthermore, al-Muqtafi also sent an army to conquer Jibal, but the army was defeated by Muhammad. In 1157, Muhammad marched to the Abbasid capital of Baghdad with an army of 30,000 men, while his ally the ZangidQutb ad-Din Mawdud marched from Mosul to capture the Caliphate's provinces in Central Iraq. On January 12, Muhammad reached the walls of western Baghdad. In response the Caliph gathered all his troops from Hillah and Wasit to defend the capital. In February, unable to defend western Baghdad, the caliph abandoned the western side and ordered all the bridges over the Tigris river, which separates the western side of Baghdad from its eastern side, to be destroyed. Muhammad crossed to the western side and easily captured it, and established his camp while at the same time the caliph fortified the walls of eastern Baghdad. Several catapults and ballistas were installed on the city's walls. The caliph also armed the natives of Baghdad by giving them armour and weapons, and incited them to fight the enemy of the caliphate, whom he called infidels since they waged war against the caliph, the successor of the prophet and the leader of the ummah. He also ordered his vizier Awn ad-Din ibn Hubayra to give 5 golden dinars to every wounded soldier. On March 4, Sultan Muhammad and his ally Zayn ad-Din, Qutb ad-Din's vizier, attacked eastern Baghdad and bombarded the city. The army of Baghdad repulsed the attack thanks to the courage of the natives of Baghdad and the naffatuns. On March 29, the Seljuks repaired one of the bridges and crossed to the eastern side of the city, where they skirmished with both the Caliph's army and the native militias of Baghdad. The naffatuns destroyed several catapults. The Seljuks tried to breach the gate by a battering ram but it was destroyed by the catapults on the walls. The result of the battle remained indecisive for both sides. On June 29, Sultan Muhammad ordered his men to climb the walls. He had already made 400 ladders to climb the walls of Baghdad, but the assault was repulsed due to the heavy fire and casualties. In the meantime Nur ad-Din Zangi blamed his brother Qutb ad-Din for attacking the caliph's realm, which destroyed the Zengid-Seljuq alliance. Zayn ad-Din lifted the siege and returned to Mosul. Muhammad also was forced to lift the siege after his men informed him that his brother Malik-Shah III has captured Hamadan. He eventually realized that the siege was useless, so he preferred to fight for his throne. Thus the Siege of Baghdad came to end on the July 13 1157. Muhammad shortly managed to repel Malik-Shah III, but became sick during this period, and eventually died in 1159 at Hamadan. The powerful amir of Ray, Ïnanch Sonqur, then put Suleiman-Shah on the Seljuq throne.
