A source told The Guardian newspaper that Abu Bakr al-Baghdadi was hit in the al-Baaj area of Nineveh, northern Iraq last month.
They also revealed al-Baghdadi's injuries are thought to be life-threatening, prompting urgent meetings among other leaders about who would succeed him if he died.
They added al-Baghdadi has been recovering from his injuries, and has still not resumed day-to-day control of IS.
An Iraqi official, Hisham al-Hashimi, has confirmed that Abu Bakr al-Baghdadi had been injured in an airstrike on March 18th. An unnamed Western diplomat has said pilots did not know al-Baghdadi was in one of the cars they were targeting when they fired.
The United States Pentagon, the headquarters of American defence operations, said it was unable to confirm whether or not Abu Bakr al-Baghdadi has been harmed or not.
A mixture of US-led airstrikes and battling on the ground by Kurdish and other forces mean approximately 20,000 square kilometres have been recaptured from IS.
Last month, Kurdish forces recaptured Saddam Hussein's hometown of Tikrit from Islamic State.
It is the first city recaptured from the extremist group, and is an important strategic victory on the way to recapturing the Islamic State stronghold of Mosul, a city in northern Iraq.