The left-handed-hitting Spears, who has ties to new manager Terry Francona, has eight career big league at-bats, all with the Red Sox over the last two seasons.
Spears spent the majority of the 2012 campaign with Boston's Triple-A affiliate in Pawtucket, where he batted .240 with 10 homers and 38 RBIs in 108 contests while playing every position except pitcher, catcher and center field.
Selected by the Orioles in the fifth round of the 2003 First-Year Player Draft, Spears made his Major League debut in 2011 for the Red Sox, with Francona as his skipper. In parts of 10 Minor League seasons with the O's, Cubs and Red Sox, the 27-year-old has accumulated a .270 batting average and .358 on-base percentage. He tallied a career-high 20 homers and 82 RBIs for Double-A Portland in 2010.
The Indians also outrighted right-handed pitcher Fabio Martinez to Triple-A Columbus. The club had designated the 23-year-old for assignment on Nov. 20.
Martinez compiled an 0-2 record and 8.53 ERA in eight appearances with Class A Carolina after the Tribe claimed him off waivers from the Angels in early August.