The ruling comes one year after South Korea's Constitutional Court ousted Park, upholding the impeachment petition brought by the National Assembly, the country's parliament, which accused her of violating the constitution by allowing Choi to meddle in national politics.
The court ruling said Choi, who was at the center of the influence peddling scandal that led to Park's impeachment in March a year ago, abused the presidential power and forced large conglomerates to donate tens of millions of US dollars to two nonprofit foundations controlled by Choi.
The court still found Lee guilty of giving 3.6 billion won ($3.3 million) in bribes for equestrian training of Choi's daughter and of embezzling the money from Samsung.
Choi already received a three-year prison term in a separate corruption case for abusing her power to get her daughter admitted to a prestigious university, despite her lacking qualifications.
Also on Tuesday, billionaire businessman Shin Dong-bin, chairman of conglomerate Lotte, was sentenced to 2.5 years in jail on related bribery charges.
She also took advantage of her ties with Park to force such companies to donate millions to institutions she then controls. Choi left the courtroom quietly after the sentencing without showing any emotion.
Samsung Electronics Vice Chairman Lee Jae-yong was released on appeal as the higher court cleared him of major charges and handed down a suspended sentence. The de-facto head of technology giant Samsung Electronics Co. was jailed previous year in a related trial but he was unexpectedly released last week on appeal, in a ruling that was perceived as a setback to government pledges to curtail the power of the nation's corporate elite. The former president has denied any wrongdoing.
The court ruling on Choi is expected to affect the sentencing of Park, slated for late March, as most of her charges occurred in collusion with the former president.
The court ruled that there had been a tacit request from Shin to win duty-free licenses from Park in exchange for W7 billion Lotte paid into Choi's bogus K-Sports Foundation. She was introduced by her father to Park years earlier.
Choi Soon-sil (L), Park Geun-hye's longtime friend and confidante; An Chong-bum (C), Park's former senior aide; and Lotte Group chairman Shin Dong-bin are shown in this composite photo on February 13, 2018 as they enter the Seoul Central District Court to attend their sentencing over the corruption that led to Park's ousting.
The disgraced ex-leader is also standing trial over the scandal, but has refused to show up in court in protest of the extension of her detention, claiming she is being made a target of "political revenge".
She was indicted on multiple charges, including bribery, a month after she was sacked as president by the top court in March.