She has also been fined 18 billion won.
The sentence handed down by a panel of three judges at the Seoul Central District Court was apparently more lenient.
Prosecutors had sought 30 years of jail-term and and a 80 million pound.
Park, who can appeal to a higher court, was not in court on Friday for the verdict. She cited sickness as the reason for not appearing for the verdict. She has boycotted the proceedings since October.
South Korea's first female leader, also became its first president to be impeached when she was ejected from office a year ago, then swiftly arrested for corruption, reported the Washington Post.
She had also denied all wrongdoing.
In an unprecedented move, the South Korean authorities permitted live broadcast of Friday's verdict.
According to the reports, Choi, who, had no government experience but was branded in a US diplomatic cable as having "complete control over Park's body and soul during her formative years".