The person spoke to The Associated Press on condition of anonymity Monday because teams can't announce moves until the new league year begins Wednesday. Terms of the deal weren't immediately known.
Speights should help fill the void left by power forward Carl Landry, who agreed to a four-year, $26 million deal with the Sacramento Kings on Sunday. 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.
He will likely come off the bench for the Warriors at both power forward and center.
Copyright 2014 Associated Press. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.