US forces say they are holding the man who helped Iraqi insurgents evade capture by changing their appearance.
Walid Muhammad Farhan Juwar al-Zubaydi, known as "The Barber", and another man were arrested on 24 September in Baghdad, said a US military statement.
The other, Ibrahim Muhammad Subhi Khayri al-Rihawi, was a "close associate" of Abu Azzam, al-Qaeda's second in command in Iraq, it said.
Abu Azzam was killed by US forces in the Iraqi capital a day or two later.
Abu Azzam is described as the top aide to Abu Musab al-Zarqawi - al-Qaeda's leader in Iraq.
The US announcement was made on the day Iraqis voted for a new constitution amid insurgent threats to disrupt the ballot.
Abu Azzam was said to be in charge of operations in Baghdad
"'The Barber's' duties included altering senior al-Qaeda in Iraq members' appearances by dying hair colour, altering hairstyles and changing facial hair in their efforts to evade capture," the US military said in the statement.
The other militant, also known as Abu Khalil, was described as "a close associate of Abu Azzam, [who] served as an executive assistant for the terrorist emir".
"He also acted as a banker for Azzam and stored the terrorist organisations' funds so they would not be confiscated should Abu Azzam be killed or captured."