Gunmen claiming to be security personnel took Afrah Shawqi al-Qaisi from her home in Baghdad.
After being freed late on Tuesday, she told NRT television: "The treated me well. They just interrogated me and thank God they found me not guilty."
Hours earlier, Prime Minister Haider al-Abadi had said investigators believed the kidnapping was both politically and criminally motivated.
Ms Qaisi, who writes for the London-based pan-Arab newspaper Asharq al-Awsat, and is also an employee of the Iraqi culture ministry, campaigns against corruption and government mismanagement.
The day before she was abducted, the 43 year old had published an article expressing anger at how armed groups were able to act with impunity.
"If the state is anxious to preserve its prestige, it should hold accountable whoever uses weapons illicitly," she wrote for the Aklaam website.
Iraq is considered one of the most dangerous places to be a journalist. Seven were killed in the country in 2016, according to press freedom group Reporters Without Borders.
A prominent Iraqi female journalist who was abducted last week has been freed.