Carter, who yesterday visited a Turkish base that has become a key hub for air raids against the jihadists, met Prime Minister Haider al-Abadi and Defence Minister Khaled al-Obeidi.
They discussed means of "improving cooperation between the two countries in the fields of arming and training," a statement from Abadi's office said.
Carter and his delegation also met US partners in the international anti-IS coalition, and were due to leave later Wednesday.
US aircraft carry out daily air strikes against IS targets, most of them in the Iraqi part of the jihadists' self-proclaimed "caliphate", which also covers regions in Syria.
President Barack Obama said on Monday the US and its allies were hitting IS "harder than ever" and warned the extremists' leaders: "You are next.