At an afternoon news conference, Mariners chairman Howard Lincoln praised Gillick as an experienced general manager, and "most important, he has a history of fielding championship teams."
For the past five weeks, the Mariners had been interviewing possible replacements for GM Woody Woodward, who announced his resignation Sept. 23.
Gillick, 62, led the Blue Jays to titles in 1992-93. He also served as general manager of the Baltimore Orioles from 1995 until his retirement after last season. He has twice been named baseball's Executive of the Year.
Gillick was the first candidate interviewed by Mariners president Chuck Armstrong. But on Oct. 7, Gillick withdrew his name, saying his wife, Doris, who runs an art gallery in Toronto, did not want to move to Seattle.
However, he reportedly reconsidered, and flew to Seattle last week to meet with Mariners officials, The Times said.
Gillick was with the Blue Jays from 1976 until he stepped down after the 1994 season.
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