The son of More Than Ready was standing at Wattle Brae Stud.
Mahisara won seven races during his career including the G3 Sandown Stakes.
Wattle Brae Stud, located on the Darling Downs, had high hopes for the stallion with his oldest progeny only four.
Wattle Brae's Garyt Turkington said his death will be a loss for the Queesland industry.
"He was just starting to get the recognition he deserved through horses like Mahis Angel, Kim Alicia and Miss Sara. I think this would have been his season," Turkington said.
Turkington confirmed that contracts had been exchanged finalizing the sale of Wattle Brae to cutting horse breeders Rick and Rebecca Knudsen, bringing an end his family's 109-year association with the Darling Downs thoroughbred property.
The Knudsens moved to secure Wattle Brae in a private sale after the stud was passed in at auction in June.