Giles spent last season with the San Diego Padres, batting .229 with four homers and 39 RBI in 116 games. He was an All-Star with Atlanta in 2003, when he hit .316 with 21 homers and 69 RBI.
In Colorado, Giles could compete for the starting second base job following the departure of Kazuo Matsui, who agreed to a $16.5 million, three-year deal with Houston last month.
Last season, Giles went 10-for-19 (.526) with two doubles in five games at Colorado's Coors Field.
The 29-year-old Giles was drafted by the Braves in 1996. He owns a .277 career batting average with 76 home runs and 187 doubles in seven major league seasons.