The Red Sox acquired Harris from the Athletics on Tuesday in exchange for right-hander Ben Hansen, Mark Feinsand of MLB.com reports.
The Athletics removed Harris from their 40-man roster last weekend, despite the fact that he slashed .336/.441/.537 with five home runs over 178 plate appearances at Triple-A Las Vegas. The Red Sox were willing to make room on their roster for Harris, who could have a chance to contribute in the big leagues at some point in the near future while the club has contended with multiple injuries in the infield. He'll report to Triple-A Worcester to begin his time in his new organization, however.