"I selected Philadelphia because they are the World Series champions and have high expectations for a playoff berth next season," Park said during a news conference in Seoul, according to The Korea Times.
The contract includes bonuses that could make the deal worth $5 million, Park said.
"Five teams have contacted me so far, and the Phillies made the biggest efforts among them," Park said.
Those teams included the San Francisco Giants, Arizona Diamondbacks, Kansas City Royals and Toronto Blue Jays, the newspaper reported.
Park, a native of South Korea, pitched 95 1/3 innings with a 3.40 ERA for the Los Angeles Dodgers in 2008 -- his 11th full major league season -- making five starts in 54 appearances.
He said the Phillies expected him to start, despite reports that have said the team sought Park to help boost their bullpen.
"I was a little worried about the Citizens Bank Park, the home of the Phillies, which is hitter-friendly, but as they considered me as a starter, I signed with Philadelphia," he said.
Philadelphia's rotation will again include Cole Hamels, Joe Blanton and Brett Myers next season, and the team announced just before 2:30 p.m. Monday that they had re-signed 46-year-old Jamie Moyer, who went 16-7 with a 3.71 ERA in 2008 with the Phillies.