Titus Day, 49, had pleaded not guilty to dozens of charges alleging he embezzled almost $900,000 owed to Sebastian through royalties, performance and ambassador fees.
But a jury on Thursday convicted him of 34 charges, while they found him not guilty of 13 charges.
Each charge carries a maximum penalty of 10 years in prison.
The Australian Idol winner on Friday told 2GB radio he was grateful the court case had finally concluded.
"It's been a pretty challenging time," he said.
"But I was just really relieved at the end because it's been four-and-a-half years of going through something very painful."
His comments were aired hours before the Crown unsuccessfully tried to have Day's bail revoked saying he broke his client's trust over a period of at least three years.
"He occupied respect of the victim and the specific trust that was placed in him in the role he performed.
"It was a special relationship in some respect".
Day's barrister Dominic Toomey SC submitted that there was scope to sentence his client to an intensive corrections order and that the judge should first proceed to a sentence hearing before imposing any jail time.
Judge Timothy Gartelmann said there was no risk that Day would not re-appear in court and dismissed a detention application.
"This doest not mean the accused will not be sentenced to full-time imprisonment nor does it mean it is unlikely," Judge Gartelmann said.
The judge ordered Day surrender his passport and report to Waverley police station once a week.
Day was found to have withheld amounts ranging from $593 to more than $174,000 in royalty and performance fees owed to Sebastian between 2013 and 2020.
The jury was told no contract was ever formalised between Day and Sebastian when he took over managing the Australian Idol winner via his company 6 Degrees between 2009 and 2017.
The pair's business relationship ended in an acrimonious split, and the pop singer filed a civil lawsuit in the Federal Court in July 2018.
Two years later he approached police when he says he discovered criminal behaviour.
The matter will next return to court on September 16.
