The Great Barrier Reef has been closely monitored for the past few years due to bleaching concerns.
The first survey for 2017 was conducted on Thursday by the Great Barrier Reef Marine Park Authority, over the area between Cairns and Townsville in northern Queensland.
The agency's David Wachenfeld said that had given him enough information to "regrettably" confirm another mass bleaching.
"We also have quite a few reports through our early warning system, the eye on the reef program," Dr Wachenfeld said.