It crashed into a ravine on the heights of Karystos, where a fire started on Sunday, according to Greek officials.
“A Greek Canadair plane, with at least two people on board, crashed near Platanisto,” a village in Evia, spokesman Yannis Artopios said.
The plane was among at least three other aircraft and around a hundred firefighters in the fight against the flames on Evia.
The two pilots missing were members of the Greek Air Force, according to information from the Greek Ministry of Defense, quoted by state TV ERT, which published a video of the aircraft as it crashed and disappeared behind a cloud of flames and black smoke.
Wildfires have been raging in Greece amid scorching temperatures, forcing mass evacuations in several tourist spots including on the islands of Rhodes and Corfu.