The deal was reached over the weekend. Ross was in Boston for a physical this week before it could be finalized.
Ross played 62 games for the Atlanta Braves last season, his 11th in the major leagues. He batted .256 with nine home runs and 23 RBIs. Atlanta went 54-35 in his starts at catcher over the past two years -- the best winning percentage for an NL catcher with at least 65 starts.
In his career, Ross has batted .238 with 84 homers and 248 RBIs.