On November 20, 1998, Ohka's contract was purchased by the Boston Red Sox from the Yokohama BayStars (Japan's Central League).

Ohka's statistics in Japan were less than flattering, but his ability to control his pitches sparked the interest of the Red Sox.

[citation needed] In 1999, Ohka began his North America professional career with the Red Sox' Double-A affiliate at that time, the Trenton Thunder.

In June 2004, Ohka's right forearm was broken when he was hit by a line drive off the bat of Carlos Beltrán in Kansas City.

[1] On June 10, 2005, the Washington Nationals traded Ohka to the Milwaukee Brewers for second baseman Junior Spivey.

In Ohka's first game with his new club on June 14, he threw a shutout against the Tampa Bay Devil Rays during interleague play.

On January 23, 2007, the right-hander reached a tentative agreement with the Toronto Blue Jays on a one-year contract.

On December 5, 2008, Ohka signed a minor league contract with the Cleveland Indians with an invitation to Spring Training.

[5] He was a non-roster invitee to spring training, but was reassigned to minor-league camp on March 2, 2014, without making an appearance.

Ohka returned to Japan and played with the Toyama Thunderbirds and Fukushima Hope of the semi-pro Baseball Challenge League for the 2015 season.