Gilberto Valle entered the plea Monday in federal court in Manhattan.
Authorities arrested the 28-year-old NYPD officer last month based on a tip from his estranged wife.
The FBI says it uncovered emails from Valle to an unidentified co-conspirator "discussing plans to kidnap, rape, torture, kill, cook and eat body parts of a number of women."
No women were actually harmed, and Valle's lawyer claims he was never a threat. She says the alleged plot was pure fantasy.
The jailed Valle is due back in court Tuesday for a bail hearing.