At the center of the allegations, Lee is accused of providing and promising some 43-point-three billion won worth of bribes to the Mir and K-Sports foundations controlled by former President Park Geun-hye's longtime confidante Choi Soon-sil.
The case has gripped the public amid growing anger against South Korea's biggest companies, known as chaebols. First arrested in February, Lee was also convicted of embezzlement, hiding assets overseas and perjury.
Council for Lee argued that his client was unaware of such activities, adding that Park exerted duress pressure for making donations.
March, 2017: Constitutional Court upholds parliament's vote to impeach Park, removing her from office.
"Apparently Park's trial will continue until October", said Vaessen. In total, Samsung was found to have paid about $7.9 million for bribery.
Samsung lawyers, meanwhile, have said that they will file an appeal against the court order. What actually happened, according to courts, is that Park pressured the state-funded National Pension Service to agree to a Cheil Industries and Samsung C&T merger in 2015.
The attempts to hide Samsung's involvement also constituted crimes, it said.
Payments were said to include $6.4m in supporting the equestrian career of Choi's daughter.
The verdict also dealt a blow to Samsung's publicly stated position that recent business dealings or restructuring efforts have nothing to do with the succession of corporate leadership to Lee from his father. Judges rejected the argument. In return for the donations, Lee would seek political favours.
Even though Lee was found guilty today it doesn't necessarily scuttle his chances for succeeding his father.
Jae-yong became the Samsung president in 2009, while in 2013 he was made the vice-chairman of Samsung Electronics, which makes smartphones, televisions, cameras and hard drives.
The ruling in Lee's case can be appealed against twice.