More than 20 students graduated from a NATO-led "train the trainers" course led by Italian military forces at Base Camp Dublin just outside Baghdad, the military alliance announced.
Baghdad asked NATO to help train the oil police to build a force that could protect the country's vital infrastructure.
Iraq gets most of its federal revenue from oil sales. Crude oil from the northern Kurdish provinces in Iraq started flowing through a pipeline to Turkey after a series of delays last week.
Oil pipelines were the target of frequent militant attacks during the height of the U.S.-led war.
Iraqi and Japanese companies met to expand oil export capacity from southern Iraqi ports from around 2.2 million barrels per day to about 5.8 million bpd.
The project includes building a 45-mile oil pipeline to terminals in the Persian Gulf. Baghdad said new international contracts could put it in a position to one day rival Saudi Arabia in terms of oil production.