Green was pleased that the rape charge was rejected and will address the ecstasy charge in court, his attorney Blair Berk wrote in a statement.
She said any sexual contact between Green and the woman was consensual.
"Mr. Green encouraged a full and complete investigation of those claims and he was confident once conducted he would be cleared of having any wrongful intent," Berk wrote. She declined further comment.
Prosecutors claim Green gave the woman ecstasy in July 2012.
Callaway is the Grammy-winning singer of the hit "Forget You" and performed as part of the duo Gnarls Barkley. He appears as a judge on NBC's "The Voice" competition show.