The man who used to run the Northern Territory Police, John McRoberts, will spend his first night behind bars in Darwin prison on Monday.
He will discover on Tuesday how long, or if, he has to stay there.
His sentencing for attempting to pervert the course of justice was delayed on Monday as his lawyer made a last-ditch bid for his freedom.
The 59-year-old was found guilty in the NT Supreme Court in Darwin last month of intending to deflect and frustrate a fraud investigation into his former lover, travel agent Alexandra Xana Kamitsis, including blocking a raid on her business.
Kamitsis was herself jailed in the NT's largest-ever fraud investigation, in which numerous Darwin travel agents were found to have been defrauding a government pensioner concession scheme of millions of taxpayer dollars.
McRoberts, the police commissioner from 2009 to 2015, was sent to Darwin prison 30km east of the CBD on Monday evening.
His lawyer Tony Elliott urged Justice Dean Mildren to give Mr McRoberts a suspended sentence and fine, meaning he would avoid jail, or home detention.
He had delayed and not stopped justice occurring and his motive was trying to protect himself from public embarrassment about the sexual affair, not to cover up a crime, Mr Elliott said.
"He was an exemplary police officer and he has made one bad decision, the bad decision is not to talk about something that would be scandalous in all the circumstances," he told the court.
"We urge upon the court that it is understandable that people sometimes make the error of trying to avoid scandal, and that is what he has done to his peril."
Justice Mildren pointed out to Mr Elliott that McRoberts was also likely trying to save his high ranking and high-paying job in avoiding having his affair revealed to detectives investigating Kamitsis.
He also rebuked Mr Elliott for asking for home detention at the last-minute during sentencing, which he said could not be considered now as it was was a complex option that took more than a month to organise.
Prosecutor Mary Chalmers said Mr McRoberts abused his power as the head of the law enforcement agency.
"Public confidence in the judicial system will be lost unless it is made clear such conduct will bring a prison sentence," she said.
The maximum jail term is 15 years.
The only other Australia police commissioner to be jailed in recent history is Queenslander Terry Lewis in the 1990s.