At least 10 rockets struck the Ain al-Asad base, located in western Anbar province, at 7:20 a.m., The Associated Press reported.
No casualties were immediately reported, according to Reuters.
The base was the same one targeted last February in an attack that left about 100 troops with head injuries, Bloomberg News reported.
Iraqi forces were leading the investigation into the attack, Col. Wayne Marotto, a U.S. military spokesman, wrote on Twitter.
The rocket fire came just days after sources told Fox News that the Combined Joint Task Force-Operation Inherent Resolve raised the threat level for U.S. troops serving in Iraq.
U.S. military officials were expecting possible retaliation after President Biden ordered airstrikes in Syria last week.
The U.S. strikes were in response to rocket fire that targeted American presence in the region. That rocket fire killed a coalition contractor from the Philippines outside an airport in Irbil, in northern Iraq, the AP reported.
U.S. officials described the Biden-ordered response as “proportionate” to the preceding rocket fire.
The source of Tuesday’s rocket fire was not immediately known.
The rocket fire also came as Pope Francis planned a historic visit to Iraq for later this week that would make him the first pontiff to ever visit the country.
The Associated Press contributed to this story.