The state's chief veterinary officer, Dr Rick Symons, said the horse had shown rapid onset of illness.
"The horse died on Tuesday and the positive result for the virus came back late last night," he said.
"The veterinarian who attended the horse used the proper precautions including the use of personal protective equipment."
Symonds said Biosecurity Queensland was in the process of quarantining the property and will test and monitor the other five horses at the location over the next month.
Dr Symons said it was unusual to get a hendra case in mid-summer.
"There was a previous case in the Townsville area in December 2004," Symonds said.
"Even though the majority of cases tend to occur in the July-September period, we have consistently said that hendra virus infection can occur throughout the year.
"Horse owners should not be complacent and as much as possible keep horses away from areas where there is flying fox [native fruit bat] activity.
"We will deal with this latest case just as we have with previous cases through a process of quarantine, testing and monitoring.
"In each hendra virus incident the property has been isolated and there has been no spread of the infection to another property."
Queensland's chief health officer, Dr Jeannette Young, said public health experts would visit the property today to assess the situation and determine how many people, if any, had contact with the infected horse.
It would undertake contact tracing work to ensure all people potentially exposed to the sick horse have been identified, Young said.