He has not been seen since 2014, when he proclaimed from Mosul the creation of a "caliphate" across parts of Syria and Iraq.
In this new footage, Baghdadi acknowledges defeat at Baghuz, the group's last stronghold in the region.
It is not clear when the video was recorded. IS says it was shot in April.
The footage was posted on the militant group's al-Furqan media network.
Baghdadi says the Easter Sunday Sri Lanka attacks were carried out as revenge for the fall of the Iraqi town of Baghuz.
