The 78-year-old boss of the money-laundering operation, Xuan Nhoung Nguyen, was sentenced to 20 months' imprisonment, but will be eligible for release after 12 months.

His daughter Teresa Thi Minh Nguyet Pham, 57, was sentenced to 14 months in prison and must serve nine months.

Nguyen's grandson-in-law, Hiep Long Phi Nguyen, 32, and Thinh Tan Truong, 50, a jeweller and business associate of the family, were both sentenced to nine months behind bars for their part in the scheme, but will eligible for release after three months.

Fairfax Media reported last week that the four dealt with cash in an "off-book" manner, covertly moving funds offshore to Vietnam on behalf of people who "deliberately sought to conceal their identity from Australian law enforcement".

The County Court heard the scheme, which was run from a money remittance company out of Nguyen's Springvale house, laundered about $16.7 million over six months in 2009 and 2010.

Prosecutor Robert Barry said Nhoung had offered to transfer clients' money overseas without the owners' details or source of the cash being recorded or reported to authorities. Clients wishing to transfer money in this way paid a higher commission.

Greg Jones, for Nhoung, told the court his client had accepted "full responsibility" for failing to meet compliance with his legal obligations and would lose his licence to operate and therefore his livelihood. Nhoung was paid about $320,000 commission, but it was found that 97 per cent of the company's transactions were recorded correctly.

All four had no prior convictions and pleaded guilty to two charges of either exporting or dealing with cash reasonably suspected of being the proceeds of crime.

In sentencing, Judge Irene Lawson said imprisonment was the only appropriate sentence due to the large sums of money involved, the quantity of transactions, each offender's specific role in the scheme and the period of time over which the offending took place.

"Money laundering threatens Australia's prosperity and undermines the integrity of the financial system and has the potential to fund criminal activities, which has the real potential to impact on community safety and wellbeing," she said.

"It can corrupt individuals and businesses as demonstrated by this offending. In sentencing you all there is a need for the court to exercise general deterrence."

Judge Lawson said harsher sentences would have been imposed were it not for their guilty pleas. She said she also took into account delays in prosecuting the charges and said the prospect of reoffending was low.