“US air defence systems shot down an armed unmanned aerial system entering Al Asad Air Base” early Friday morning, the coalition said in a statement.
“There are no reported injuries or damage and all coalition personnel are accounted for,” it said, adding that the incident was “under investigation”.
The base, which is controlled by Iraq, is located in the desert in the western Anbar province.
The attack comes after four US troops were hurt Thursday when rockets were fired at a base housing American forces in neighbouring Syria’s Deir Ezzor province.
Dozens of rocket and armed drone attacks have targeted US troops and interests in Iraq in recent months.
Western officials have blamed hard-line pro-Iran factions for the attacks, which have never been claimed.
But roughly 2,500 American soldiers and 1,000 coalition soldiers remain deployed in three Iraqi-controlled bases across the country, including Ain Al-Asad, to offer training, advice and assistance to national forces.