The 23-year-old man died shortly after being airlifted to hospital in a critical condition from the Pitch Arts and Music Festival in Mafeking, west of Ararat in the Grampians.
Another man in his 20s and a man in his 30s were also rushed to hospital in stable conditions from the same event.
The music festival was cancelled yesterday amid heat and fire danger warnings.
All revellers were told to leave by this morning.
The Victorian Greens said the latest suspected overdose highlighted the importance of pill testing in the community and at events.
“How many more overdoses need to happen in Victoria before the new Premier shifts gears and finally sets up pill testing in Victoria? Greens drug harm reduction spokesperson Aiv Puglielli said.
“While this Labor Government continues to stall, young Victorian lives are being put at risk.
“Even with pure MDMA we’ve seen how extreme heat can deal a deadly blow. So with untested drugs circulating, this was truly a disaster waiting to happen.”
Puglielli said the government could not afford to delay pill testing from being rolled out.
“It’s taking an already dangerous situation and turning it lethal,” he said.
“If we want to prevent more overdoses we need pill testing established on-site at music festivals as a matter of urgency.”
“There are no current plans to change the policy setting on drug checking,” she said in January.