Mohanad Shareef Hammadi, 25, received his sentence hours after Waad Ramadan Alwan was given a lesser sentence.
Co-defendant Alwan, 30, also an Iraqi, received a 40-year sentence after he agreed to co-operate with prosecutors.
The two men were arrested in May 2011 and pleaded guilty last year to conspiring to help al-Qaeda in Iraq.
They admitted using improvised explosive devices against US soldiers in Iraq were also accused of plotting to send weapons and money to the organisation.
Hammadi, who testified during the trial, said he had been raised in poverty and that life was forever changed after the US invasion of Iraq in 2003.
But prosecutors accused him of changing his account in order to secure a shorter sentence.
Alwan could have received a sentence of up to life in prison.
An Iraqi man has been sentenced to life in prison in the US state of Kentucky after pleading guilty to charges related to terrorism.