A statement issued by the agency said the one-week mission is "part of UNHCR's overall efforts to strengthen its protection and assistance programmes for hundreds of thousands of uprooted Iraqis in the region".
Okoth-Obbo will be in Syria until Tuesday, then travels to Lebanon through Wednesday, and then Jordan on Thursday and Friday. He will meet government officials and aid workers in each country.
UNHCR estimates Syria hosts about 1 million Iraqis and Jordan hosts about 750,000. Lebanon has an estimated 40,000 Iraqis.
The statement said: "Missions will be focussed on the ongoing effort to ensure that Iraqis fleeing their homeland receive international protection, that the required systems are in place ... and that there are programmes for the provision of assistance and solutions, including resettlement of the most vulnerable."Radhouane Nouicer, UNHCR's director for the Middle East and North Africa will also be reviewing operations in the region.