The clubs announced the deal at baseball’s annual winter meetings.
Mazara, 24, has tantalizing power but produced mixed results over his first four big league seasons. The 6-foot-4 slugger batted .268 with 19 home runs, 66 RBIs and a .786 OPS this year.
“He looks like he’s 7-foot every time I see him in the box,” White Sox manager Rick Renteria said earlier Tuesday. “Runs extremely well for a big guy. Can defend. Good arm. Brings a lot of qualities to the plate. Can pop one in the seats as quickly as anybody.”
Mazara projects to make about $5.5 million in arbitration and is eligible for free agency after the 2021 season.
Walker was a second-round draft pick out of the University of Oklahoma in 2018. He batted .284 with 10 homers and 62 RBIs across two Class A teams in his first full pro season.
“He is a really good hitter, with both power and an advanced approach, and has an aggressive, winning, on-field makeup,” said Jon Daniels, Texas’ president of baseball operations.