Atwar Bahjat was arrested while she was covering two explosions in al-Ghazalya district of capital Baghdad.
Cameraman Yasser Bahjat, who was with the journalist, was also taken into custody.
Both Atwar and Yasser were taken to the US forces headquarters in al-Ghazalya. Latest reports from Baghdad suggested that US forces were "investigating" them.
The day's arrests were only the latest in a long line of intimidation and harassment that Aljazeera's correspondents and crew have repeatedly been subjected to in Iraq and elsewhere.
In the last two years, the Arabic network has often come under attack for its uncompromising reporting.
The offensive against Aljazeera has varied from physical attacks to leveling of unsubstantiated accusations.
Taysir Alouni, the network's celebrated war-correspondent, is currently under arrest in Spain for alleged links to al-Qaida.
Aljazeera has dubbed his arrest as "an attack on press freedom."
Aljazeera correspondent Tariq Ayoub was killed in Baghdad when US shells struck the Aljazeera office during the Iraq war.
US troops had trained their guns on the network even during their campaign in Afghanistan.
The network's office in Kabul was bombed, shortly after the Aljazeera crew received a tip-off to evacuate the building.