General manager John Hammond said Tuesday that Mitchell was signed to a 10-day contract. Mitchell spent much of the last two seasons with Milwaukee's D-League affiliate in Fort Wayne.
The Bucks could use another scorer at small forward after buying out the contract of veteran Caron Butler. The 6-foot-6 Mitchell was averaging 19.4 points and 5.2 rebounds after returning to Fort Wayne in January. He played in China in the fall.
Mitchell averaged 21.9 points and 6.4 rebounds at Fort Wayne in 2012-13, when he won top rookie honors. He's also a two-time champion of the D-League slam dunk contest.
Mitchell went undrafted out of Alabama in 2012.