"We declare Saturday, Jan. 24 a day of national mourning for Saudi King Abdullah bin Abdulaziz," the Turkish Prime Ministry said in a statement issued Friday.
"We would also like to take this opportunity to extend our sincere condolences to the people of Saudi Arabia, and the Muslim world. May God's mercy be upon him," it said.
The national flag will be flown at half-mast across Turkey and at foreign delegations on Saturday, it added.
Crown Prince Salman bin Abdulaziz has been declared as the new king of the oil-rich Gulf monarchy and Prince Muqrin bin Abdulaziz as the new Crown Prince.
Abdullah was recently admitted to hospital and placed on a ventilator after he was diagnosed with pneumonia.
Abdullah had undergone back surgery in November 2012. Since then, he refrained from attending events outside the kingdom, including a recent high-profile Gulf summit held in the Qatari capital, Doha.
Salman, 79, is a half-brother of the deceased king. He was appointed crown prince in June 2012 after the death of the late crown prince, Naif.
Muqrin is also a half-brother of Abdullah and the youngest son of the founder of Saudi Arabia. He was serving as second deputy prime minister and the king's special envoy.