The appeals court said Kim had taken part in manipulating the price of a thinly traded Korean stock with multiple traders, reversing a lower court's ruling that acquitted Kim of the charge.
It also found that Kim accepted two Chanel bags and a Graff necklace, worth 80 million won ($A76,000) in total, from the Unification Church while aware the church expected political favours for its overseas business.
"Kim exerted her influence as first lady and committed the bribery," the lead judge said.
"She damaged public trust in government transparency and caused a rift in public opinion over national affairs."
The court also fined Kim 70 million won and ordered the confiscation of the necklace.
Kim, the wife of ousted president Yoon Suk-yeol, was sentenced to 20 months in the first ruling in January for bribery, while a court cleared her of other charges.
Along with bribery, Kim was also charged with manipulating small-cap stocks and illegally backing a candidate in a 2022 by-election.
The appellate court upheld the ruling that Kim was not guilty of breaching the election law.
Kim, who has been detained in jail since August.
She has denied all the charges and her lawyers said Kim would appeal Tuesday's ruling at the Supreme Court.
The case is among a series of trials stemming from investigations into Yoon's brief imposition of martial law in 2024 and related scandals involving the once-powerful couple.
Yoon, who was removed in April 2025, was sentenced to life in prison in February for masterminding an insurrection tied to his imposing martial law in 2024.
Several of his aides are also on trial over their alleged involvement.
Former prime minister Han Duck-soo received a 23-year jail sentence as judges ruled he "turned a blind eye" to Yoon's plan.
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