“We have determined that there is sufficient evidence for a realistic prospect of conviction,” Baljit Ubhey, London chief crown prosecutor, said.
The 25-year-old was arrested in June after The Sun claimed she introduced a journalist to a drug supplier.
It was claimed half an ounce of cocaine changed hands as a result of the deal.
Ms Contostavlos will appear before Westminster Magistrates’ Court on 19 December.
The N-Dubz member was a judge on ITV’s The X Factor from 2011 to 2012.