The iconic seven tonnes structure unveiled in 2002 was among 150 "Big Things" erected as tourist attractions across Australia.
"It looks like it was sort of two o'clock this morning-type thing. There was some heavy equipment and it looks like they've taken the mango," Bowen Tourism chairman McLaughlin told the Australian media.
He said the surveillance footage was being analysed and expressed hope that the plundered fruit would soon be found.
"I think it'll definitely turn up, no doubt about that. We're not sure what has happened but I'm sure we'll get it back."
Bowen is known as the mango production capital of Australia.