Simpson entered the plea on Monday in Kenton County Circuit Court in Covington. A grand jury indicted the four-year veteran on one count of marijuana trafficking in excess of 8 ounces on Jan. 19.
Simpson has been under investigation since September when agents from California tracked a package shipped to his northern Kentucky home. They said it contained 2½ pounds of marijuana. Authorities said a search of Simpson's home also turned up 6 more pounds of marijuana, smoking pipes and scales.
The 2008 second-round draft pick from Coastal Carolina caught 53 passes for 758 yards and four touchdowns this season. Simpson can become a free agent after completing the final year of his contract.