[5] Within the final years of Mehmed's sultanate, the rivalry of Halime and Handan continued to increase into a fierce competition.

In the end, Mehmed, under pressure from Safiye Sultan, executed Prince Mahmud, in 1603, making Şehzade Ahmed the heir and Handan his Bas Hatun.

[7] Soon after his succession, Ahmed wanted to express his gratitude to Mehmed Pasha and Gevherhan Sultan for the role they had played in bringing his parents together.

[9][5][verification needed] The administrative level formed by Handan Sultan carried out an effective policy in the first years of her son's reign.

As the Valide Sultan, Handan protected the life of Şehzade Mustafa (second son of her ancient rival Halime), who was mentally ill, and the decision whether or not to kill him because of the law of fratricide was continually postponed by Handan: in November 1604, Şehzade Osman, first son of Ahmed I, was born, definitively dropping out his possible killing.

[13] As a co-regent, she immediately began building up her network of clients, and was actively involved in the running of dynastic and imperial affairs together with Ahmed's tutor Mustafa Efendi (died 1607 or 1608).

It seems that Handan Sultan and Mustafa Efendi advised him to behave in this manner in order to give the public the impression that he was capable of ruling the state.

[16] He also began to spend a great deal of time outside the palace, notably hunting or conducting incognito inspections, regardless of the weather.

Handan Sultan quickly realized that her son could easily put himself in danger and thus needed to be closely watched.

[21] In August 1604, Ahmed ordered the execution of deputy grand vizier Kasim Pasha, and in January 1605 of his successor Sarıkçı Mustafa Pasha, and in both cases his decision was approved and encouraged by Handan Sultan and Mustafa Efendi, who were trying to rid the court of clients of Safiye Sultan.

[25] The contemporary historian Ibrahim Peçevi questioned her wisdom, but legitimized her authority over her son by an old and popular saying "a mother's right is God's right".

[36] Handan Sultan died at the Topkapı Palace on Wednesday, 9 November 1605 after a long illness, possibly a stomach disease.

[44][28] Ahmed despite appeals of the viziers for the customary mourning for seven days, didn't postpone his departure from Istanbul on campaign against the Jelali revolts.