The South Australian government has requested a review of the decision to grant James Vlassakis parole.
Vlassakis has spent 26 years behind bars after pleading guilty to being involved in four of the 11 murders between 1992 and 1999.
Parole Administrative Review Commissioner Michael David KC confirmed to AAP an appeal had been lodged.
A directions hearing on the review will be called in the coming weeks.
SA's parole board approved Vlassakis's application to serve the remainder of his life sentence under conditions in the community in August.
The attorney general, the commissioner for victims rights and the police commissioner had 60 days to apply for a review.
Vlassakis, now in his mid 40s, was 18 when he became involved in the killings in 1998 and was sentenced to life with a minimum term of 26 years, which expired in August this year.
Parole Board chief Frances Nelson previously said Vlassakis did not represent a risk to the community and would be sent to the Adelaide pre-release centre for up to 12 months and undergo a resocialisation process.
Snowtown murders accomplice Mark Ray Haydon, 66, was released on parole in May 2024 to live in the community under strict supervision.
Vlassakis was also a key prosecution witness against John Bunting and Robert Wagner, who were found guilty of 11 and 10 murders respectively.
The bodies of eight of their victims were found dismembered in barrels inside a disused bank vault in Snowtown, north of Adelaide, in 1999.
Both Wagner and Bunting are serving life sentences with no chance of parole.
In July, Haydon appeared in the SA Supreme Court, where an application for an extended supervision order for a high-risk offender was approved, and most of the conditions of an interim order imposed in 2024 were confirmed.
He spent 25 years in jail for his role as an accessory in the murder spree.
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