Cory Breton and Iuliana Triscaru were locked in a toolbox for hour before it was dumped in a lagoon.
A judge described their 2016 killings as an "unspeakable evil of the worst kind".
In 2021, Trent Michael Thrupp, Davy Malu Junior Taiao and Stou Daniels were each found guilty of two counts of murder.
Three years later, the trio have had their murder convictions overturned after a Queensland Court of Appeal ruled there had been a miscarriage of justice.
They will receive new trials following the successful appeals on Tuesday.
The trio had been sentenced to life in prison after being found guilty by a jury in 2021.
The court was told Mr Breton, 28, and Ms Triscaru, 31, were separately lured to a Kingston unit, south of Brisbane, late one morning in January 2016.
The pair were tortured, assaulted and bound with tape and zip ties before being locked in the toolbox that was about two metres long, 40cm wide and 60cm deep.
More than two weeks later, police divers found the box weighed down by concrete blocks and tyres in nearby Scrubby Creek Lagoon.
The Court of Appeal on Tuesday ordered the murder convictions for Thrupp, Taiao and Daniels be set aside and that they receive new trials.
However, the trio's appeal against torture charges was dismissed.
The Court of Appeal decision ruled there had been a miscarriage of justice on grounds including how the jury was directed in relation to the offences of murder.
The appeal was assessed by Justice Debra Mullins, Justice John Bond, and Justice Mark Livesey.
Another man jailed over what had been dubbed the "toolbox murders" also had his convictions overturned this month.
Waylon Ngaketo Cowan Walker was acquitted of murder but found guilty of two counts of manslaughter in 2021 and sentenced to 12 years' imprisonment.
Queensland Court of Appeal this month ordered verdicts of acquittal be entered for Walker's two manslaughter convictions.
