Sulaiman Al Fahim, who also fronted the Abu Dhabi United Group’s deal to buy Manchester City in 2008, was found guilty of forgery, using forged documents and aiding and abetting.
He and an accomplice were found to have stolen the money used to buy Pompey from Sacha Gaydamak, with Al Fahim soon selling the club to Ali Al Faraj.
Al Fahim, 42, did not attend the hearing and was sentenced in his absence.
Prosecutors said that Al Fahim’s wife discovered the money was missing after the returns she had expected from a high interest rate account she opened in 2009 did not come in.
She said she contacted the bank’s accounts manager, but he “kept stalling” despite her asking him to move the account in September 2011.
When she decided to visit the bank in person, she was told there was no money in the account.
She then went to the bank’s legal affairs department, and when they failed to take action she reported the matter to the police.
Dubai Criminal Court also convicted the bank manager of theft, forgery of official documents and use of forged official documents. He was also sentenced to five years in prison.
At the time of Al Fahim’s ownership, Portsmouth were in the Premier League but the club was also in financial difficulty and had struggled to pay players and staff.
Four years later, Pompey had gone into administration twice, suffered three relegations and had seven different owners.
In 2013, it was taken over by the Pompey Supporters Trust (PST), who sold it to former Disney chief executive Michael Eisner in August 2017.
Last season the club was promoted from League Two to League One. They are currently ninth in the table.
In a 2009 interview with Radio Solent conducted after he had bought Portsmouth, Al Fahim said: “To be realistic we need a new ground and we want to strengthen the squad and the academy.
“Hopefully we can have a new stadium in place by 2015 or 16. We would like to be a top-eight club by that time.”
PST spokesperson Ashley Brown told BBC Sport the case “once again raises questions about how owners can purchase football clubs”.
The Premier League has tightened its rules on ownership since Al Fahim’s brief spell, and stricter criteria now have to be met than at the time of his takeover – with changes introduced largely as a result of the club’s tumultuous ownership history.