The 22-year-old was escorted from the theme park's hotel after fellow guests complained about a "funny smell" coming from his room, according to reports.
An Alton Towers spokesperson told Sky News: "We can confirm a guest was asked to leave."
It is understood that Dappy was staying at the hotel with girlfriend Faye Vassell and fellow hip-hop musician Fearless.
A spokesman for the star insisted that the trio had only been smoking cigarettes in the room.
The cannabis allegation comes just two days after Dappy made a public apology for using the drug mephedrone.