The agreement is conditional on Ohka passing a physical exam, which will take place later this week once arrangements are made for him to travel to Toronto from his home in Japan.
Agent Jim Masteralexis declined to reveal contract terms. He said Ohka turned down a pair of two-year offers to sign with Toronto, in hopes of re-establishing his value and signing another deal with the Blue Jays or going back out on the market as a free agent next winter.
Ohka has a 48-58 record with a 4.04 ERA in parts of eight seasons with Boston, Montreal/Washington and Milwaukee. He threw only 97 innings last year with the Brewers because of injuries to his shoulder and hamstring.
"We took less money on a one-year basis to play with a competitive club like the Blue Jays," Masteralexis said. "Tomo has never had run support in his career. We think with a good club that scores runs, he can demonstrate he's healthy and prove his mettle."
The Blue Jays have Roy Halladay, A.J. Burnett and Gustavo Chacin as their projected 1-3 starters. Ohka will compete for a spot in the rotation with John Thomson, Casey Janssen, Shaun Marcum and Dustin McGowan.
Toronto pursued free agents Ted Lilly and Gil Meche earlier this winter, but Lilly left the Blue Jays for the Cubs and Meche signed a five-year, $55 million deal with Kansas City.
The Nationals, Mets and Pirates were among the other clubs that expressed interest in Ohka this winter.
Jerry Crasnick covers Major League Baseball for ESPN Insider.