Doug was found with pellet wounds to his ribs and abdomen at the base of a tree at a Morayfield property, north of Brisbane, on Tuesday morning.
His mother Meryl was also shot but is expected to make a full recovery after earlier surgery.
News that makes sense
Your trusted source for staying up-to-date with the world around you. Get free daily news updates and analysis, straight to your inbox.
Staff at the Australian Wildlife Hospital tried to remove half of one of Doug's lungs after a pellet was found in his chest.
"However, it is with sad regret that during surgery, Doug passed away and vets were unable to save him," a spokeswoman said.
X-rays on Friday revealed surgery was needed as soon as possible after it was found his condition had worsened.
He was given only a 50-50 chance of survival before the operation.
Authorities are continuing to search for the person who shot the mother-and-baby koalas.
