Miller pleaded guilty in March to two counts of supplying a commercial quantity of a prohibited drug.
He is currently behind bars and scheduled for sentence in Sydney's Downing Centre District Court along with two co-accused Wayne Allan Johnson and Justin Szabolics on Thursday.
In February 2021, the then 45-year-old swimmer was arrested one month after crystal methylamphetamine was found concealed in eight candles.
With each candle containing 500 grams of the drug, police estimated the total haul could have sold on the streets for more than $2 million.
While one charge against Miller of knowingly directing a criminal group was withdrawn, he has admitted participating in a criminal group.
He will also be sentenced for one charge of dealing with the proceeds of crime, less than $100,000.
Johnson, who is out on bail, is facing one charge of participating in a criminal group, two charges of possessing a prohibited drug, and one charge of taking part in the supply of a prohibited drug.
Szabolics is in custody and faces one charge of supplying a large commercial quantity of a prohibited drug and one charge of participating in a criminal group.
A fourth man Luke Mathew Peake was sentenced to a maximum term of imprisonment of two years and six months in March this year for his role in the drug syndicate. His 15-month non-parole period ended on May 13.
Police previously said the drugs, from Sydney, were bound for regional NSW.
Miller won silver and bronze at the 1996 Atlanta Olympics and was briefly married to Sydney model Charlotte Dawson.
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