He was signed by the Los Angeles Dodgers as an amateur free agent in 1994, at the time a sophomore at Hanyang University in Seoul. A fastball pitcher, Chan Ho Park enjoyed success with the Dodgers who played at the pitcher-friendly Dodger Stadium. He had his best season with the Dodgers in 2000, when he went 18-10 with a 3.27 ERA and 217 strikeouts.

Following a 15-11 season with the Dodgers in 2001, Park was granted free agency and was signed by the Texas Rangers in December of that year to a five year, USD $65 million contract, which is one of the highest paid contracts for a pitcher. However, during his time with the Rangers, he was hampered by injuries and a home stadium that notoriously favors hitters at Ameriquest Field in Arlington. In his first season with the Rangers, Chan Ho Park only went 9-8 in 25 starts, with a 5.75 ERA. The following season, he only started seven times due to injuries, going 1-3 with a 7.58 ERA.

Chan Ho proved to be largely unpopular with the local crowds and Dallas-area media (referred to by some media members as "Heave Ho Park" and "Oh No Park"), considering the underperforming pitcher and his large contract to be a waste of money that hampered the team. However, they did not necessarily consider Park to be a player who could no longer succeed anywhere, but rather a player who did not fit the Rangers' organization, which traditionally focused on offense and power pitchers. Under this theory, it was Park's pitching style, which tended to induce flyballs (which at hitter friendly Ameriquest often end up as home runs), which led to his troubles with the Rangers -- and which was less of a problem when he pitched for the Dodgers, with their pitcher-friendly home park Dodger Stadium. (This theory appears to be supported by evidence; From 2002 to 2004, Park had a 6.75 ERA at home, much higher than his 4.92 ERA on the road.)

Nevertheless, Park remained a popular player in his native South Korea, with many Koreans following Los Angeles Dodgers and Texas Rangers games where Park pitched. Park's place in the annals of baseball history is secure, in any case, as the pitcher who gave up Barry Bonds' record-breaking 71st home run in 2001.

On April 23, 1999, he surrendered two grand slams to Fernando Tatis in the same inning. Tatis is the only player ever to have accomplished this feat.

On June 4, 2005, Park became the first South Korean to ever reach 100 Career Wins in the majors. He was 26 days short of his 32nd birthday when he reached the milestone.

On July 29, 2005, he was traded by the Rangers to the San Diego Padres in exchange for Phil Nevin. He was shelled in his first outing as a Padre, giving up 7 runs and 5 earned runs in 4 1/3 innings with 8 hits and 3 walks against him. However, Park had a successful home debut as a Padre, including striking out a season-high eight in 5 2/3 innings of work. Padres fans hope that Chan Ho can repeat his success with the Dodgers as he plays in pitcher-friendly PETCO Park.

In the World Baseball Classic, Chan Ho Park pitched extremely well, earning 3 saves. The WBC rules for pitching forced him to be excluded in the game against Japan, which received criticism from Koreans. Though his Korean team lost to Japan in the semifinals, he finished without giving up 1 run (earned or unearned), and collected 3 saves.

He will be the fifth starter for the Padres.