Wilson, 33, hit .249 in 62 games for Seattle this season with eight doubles and 11 RBIs.
The veteran opened the season as the Mariners' starting second baseman after losing his shortstop role to Brendan Ryan in Spring Training. But Adam Kennedy largely took over the second-base job until rookie Dustin Ackley's mid-June promotion, leaving Wilson to a utility role.
"We've obviously got some young players who need to continue playing," manager Eric Wedge said. "And we've got [Justin] Smoak coming back, [Chone] Figgins coming back at some point in time. It's an opportunity to loosen things up, but it's also an opportunity for Jack to go somewhere and play in the postseason."
An excellent defender, Wilson wound up playing 45 games at second, 13 at shortstop and one at third base for the Mariners before injuring his heel on Aug. 16 after a six-game stretch during which he'd gone 10-for-22 with four doubles and four RBIs.
Wilson was acquired by the Mariners on July 29, 2009, and wound up hitting .243 in 154 games for Seattle. He's a career .266 hitter in 1,313 games with the Pirates and Mariners.
By being acquired prior to Aug. 31 means Wilson will be eligible for the Braves' postseason roster.