BAGHDAD—President Donald Trump’s senior adviser and son-in-law Jared Kushner paid a surprise visit to Iraqi Prime Minister Haider al-Abadi and other officials here Monday, receiving military briefings on the fight against Islamic State.

Mr. Kushner is the first member of the president’s inner circle to visit Iraq, a key ally in the fight against Islamic State, since Mr. Trump took office. He was invited here by the chairman of the U.S. Joint Chiefs of Staff, Gen. Joe Dunford, who is on a routine visit to meet with U.S. and Iraqi commanders and troops.

The visit comes as the Trump administration is assessing the U.S. strategy to combat Islamic State in Iraq, Syria and elsewhere.

According to a statement from Mr. Abadi’s office, the two sides discussed the battle in Mosul, international support for Iraq, as well as training and equipment issues.

The U.S. delegation also met with Irfan al-Hayali, the defense minister, and Gen. Othman al-Ghanimi, the chief of staff of the Iraqi forces.