Chief biosecurity officer Dr Jim Thompson said a horse had shown rapid onset of illness typical of Hendra virus infection.
The horse was under veterinary care but died on Friday, Thompson said. The animal has been buried.
Thompson said Biosecurity Queensland was finalising test results, expected to be known later today.
"We are announcing this suspect case because we are aware that there have been some concerns raised in the Chinchilla area due to horse events being held today.
"If the results are positive, the property will be quarantined as we understand there are four other horses on the property," he said.
"We have already been in contact with the owner and vet. If quarantined, horses will be restricted from moving on or off this property but there will be no general movement restrictions on horses in the Chinchilla area."
Queensland Health chief health officer Dr Jeannette Young said staff would arrive on the property today to assess the situation.
It is not yet known how many people have been potentially exposed.
The latest death from Hendra, if confirmed, takes the toll to 10 in Queensland and four in New South Wales.