The announcement Friday gives Golden State another versatile power forward off the bench whom they hope can fill the void left by Carl Landry, who agreed to a four-year, $26 million contract with the Sacramento Kings last Saturday.
Speights averaged 10.2 points and 5.1 rebounds in the final 39 games with Cleveland after coming over in a trade from Memphis last season.
Speights' deal is for three years and about $11 million. The third year is a team option.
The 25-year-old Speights was drafted 16th overall out of Florida by Philadelphia in 2008. He has averaged 7.8 points and 4.4 rebounds in his first five NBA seasons.