FanRag Sports' Jon Heyman reported the two sides agreed to a two-year deal worth $6 million. According to Heyman, Jackson can earn another $2.5 million based on achieving certain incentives.
Jackson is the second outfielder the Giants have added this offseason after acquiring Andrew McCutchen from the Pittsburgh Pirates.
Jackson began last season by signing a minor-league deal with the Cleveland Indians in January. The 30-year-old struggled his way to a .254/.318/.343 slash line in just 54 games with the Chicago White Sox in 2016.
After making Cleveland's 25-man roster out of spring training, Jackson became an invaluable member of manager Terry Francona's lineup. He set career highs in batting average (.318), on-base percentage (.387) and slugging percentage (.482).
Francona acknowledged Jackson's importance in Cleveland's lineup after All-Star Michael Brantley injured his ankle in early August.
"Austin has really, really picked us up a number of times," Francona said, via Cleveland.com's Zack Meisel. "You lose a Brantley, that's not good. And certainly, long-term, it's not. But when you look up at what A.J. has done, he's been so good. So, he's taken some of the sting away."
Jackson is a player who has to be carefully managed to maximize his performance. He only appeared in 85 games for the Indians last season due to two stints on the disabled list.
His best asset is his hitting ability versus left-handed pitching, whom he posted a 1.013 OPS in 2017. The Giants will have to closely watch Jackson to make sure he's not overextending himself physically. He hasn't played more than 120 games in a season since 2015.
When Jackson is healthy and on the field, he's a versatile outfielder who can play all three positions and has a potent bat to hit anywhere in the order to give the Giants a deeper lineup that will score a lot of runs.