Upton joins the Braves after spending his first eight major league seasons with the Tampa Bay Rays. He hit .246 with 28 homers, 78 RBIs and 31 steals this year.
Upton, who was to be introduced at a news conference Thursday, replaces free agent Michael Bourn in center field and should provide needed power from the right side.
The addition of Upton leaves Atlanta still needing to fill left field. Martin Prado is expected to move to third base, taking over for the retired Chipper Jones.