The 42-year-old rap star, who is on tour with Florida Georgia Line, had performed with the country band at the White River Amphitheater hours earlier.
Nelly’s lawyer refuted the accusation.
“Nelly is the victim of a completely fabricated allegation,” said attorney Scott Rosenblum in a statement released to Page Six.
“Our initial investigation, clearly establishes, this allegation is devoid of credibility and is motivated by greed and vindictiveness.
“I am confident, once this scurrilous accusation is thoroughly investigated, there will be no charges.
“Nelly is prepared to address and pursue all legal avenues to redress any damage caused by this clearly false allegation.”
The band and Nelly were scheduled to perform Saturday night in Ridgefield, Washington.