The attack took place in the evening when the rockets landed on the air base, located around 90 km from Iraqi capital Baghdad, wounding two soldiers and causing damages to nearby buildings, a security source told Xinhua news agency on the condition of anonymity.
Balad air base is the largest military air base in Iraq, also known by the US forces as the Logistics Support Activity (LSA) Anaconda.
The air base was housing a number of US troops and advisors of an American company operating the Iraqi F-16 jet fighters, but they withdrew about a week ago after the international US-led coalition announced the suspension of its operations against the Islamic State (IS) militants in Iraq.
No group has so far claimed responsibility for the attack.
The attack came a few days after Qais al-Khazali, leader of the Iraqi Iran-backed Shiite militia Asa'ib Ahl al-Haq, said the Iranian initial response to the killing of the Iranian military leader is done and it is time for Iraq to respond to the US airstrike.
Al-Khazali's threat came after Iran fired ballistic missiles earlier in the day on military bases housing US troops in Iraq's western province of Anbar and near the city of Erbil, capital of the semi-autonomous region of Kurdistan.
Last week, a US drone attacked a convoy at Baghdad International Airport, killing Qassem Soleimani, commander of the Quds Force of Iran's Islamic Revolution Guards Corps, and Abu Mahdi al-Muhandis, deputy chief of Iraq's paramilitary Hashd Shaabi forces.
More than 5,000 US troops have been deployed in Iraq to support the Iraqi forces in the battles against Islamic State militants.
( With inputs from IANS )