Saito, who turns 40 in February, is the second reliever signed by the Braves in as many days after they added veteran closer Billy Wagner to the roster on Wednesday.
"While we primarily expect him to pitch in the eighth inning, this allows us to have another pitcher with 'closer' ability who can compliment Billy Wagner, similar to the depth we had in 2009."
Braves manager Bobby Cox said: "This is a great acquisition. From what we experienced when we faced him with the Dodgers, Takashi really shortens the game -- we knew we had to score runs early because he was 'lights out' when he came in late in the game."
Saito, a 2007 National League All-Star with the Dodgers, has a 15-10 career MLB record with 83 saves in 95 chances and a 2.05 ERA in 236 games.
With Boston, Saito was 3-3 with two saves and a 2.43 earned run average in 55 and two-thirds innings.
Before coming to Major League Baseball, Saito played for the Yokohama Bay Stars of the Japanese Central League from 1992 to 2005, compiling an 87-80 record with a 3.81 ERA and 48 saves as a starter and reliever.
(Writing by Larry Fine in New York, Editing by Clare Fallon)