Stewart and the Pirates then agreed to a $1 million, one-year deal.
The 31-year-old Stewart hit .211 with four home runs and 25 RBIs in a career-high 109 games for New York in 2013. He threw out 17 runners, the fifth-highest total in the American League.
To make room for Stewart on the 40-man roster, the Pirates designated catcher Mike McKenry for assignment. McKenry hit .217 in 41 games last season for Pittsburgh before tearing cartilage in his left knee in July.
Stewart because expendable to the Yankees when they agreed Nov. 23 to an $85 million, five-year contract with Brian McCann, a deal likely to be finalized this week. After making $515,100 this year, Stewart is eligible for salary arbitration for the first time.
Teams faced a midnight deadline to offer 2014 contracts to unsigned players on their 40-man rosters.
Francisco Cervelli, who figures to be the McCann's backup, didn't play after April 26 because of a broken hand. He also served a 50-game drug suspension.