Green, whose real name is Thomas DeCarlo Callaway, pleaded not guilty to one felony count of furnishing a controlled substance just hours after prosecutors charged him.
The singer sat in a front row of the courtroom with his girlfriend while waiting for a bondsman to post his $30,000 bail.
He is accused of slipping the drug Ecstasy to a woman as they dined in downtown Los Angeles in July 2012.
The two later went back to the 33-year-old woman's hotel room. Prosecutors declined to file a charge of rape of an intoxicated person, citing insufficient evidence.
Green's attorney Blair Berk said any sexual contact between her client 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 in a statement.
Green is due back in court on Nov. 20. If convicted, the 39-year-old entertainer faces up to four years in state prison.
Green is known for hits like "Forget You" and for his appearances as a judge on the TV talent show, "The Voice."
The Associated Press contributed to this report.