Donald Tsang, who was Chief Executive from 2005 to 2012, was jailed by the High Court for 20 months after he was found guilty by a jury of misconduct in public office, according to broadcaster RTHK
The charges stem from a luxury penthouse in Shenzhen, across the Chinese border, that the 72-year-old former leader intended to use as a retirement home.
According to RTHK, Justice Andrew Chan told the court the seriousness of the case was due to Tsang's high position and the "breach of trust was an important and significant aspect in his criminality."
The sentencing comes after around 40 high profile Hong Kongers wrote letters in support of Tsang
and calling for leniency, including the two frontrunners to be the city's next Chief Executive
Tsang also faces a potential retrial in September, after the jury failed to reach a verdict on a separate charge of bribery.
Tsang was accused of having a conflict of interest over the purchase of the flat, which he did not reveal.
While in negotiation with property tycoon Bill Wong to buy the apartment, Tsang approved a digital broadcast license, and other requests, from Wave Media, in which Wong held a 20% stake.
Last week, a jury found that Tsang had deliberately concealed his negotiations with Wong and found him guilty of "misconduct in public office."
The offense, which stems from the common law, "is a key weapon in the fight against corruption in Hong Kong," according to Valarie Fung and Catherine Leung
of law firm Norton Rose Fulbright.
"It encompasses any serious misuse of power or position by public officials even in the absence of evidence that they have received a bribe."
Tsang's is the second high-profile case in Hong Kong this month. Last week, seven police officers were found guilty of assaulting a protester
during the 2014 pro-democracy Umbrella Movement demonstrations.