Gilberto Valle entered the plea Monday in federal court in Manhattan.
Defense lawyer Julia Gatto called the accusations against her client "exaggerated," saying Valle participated in one of thousands of fetish chat rooms online in which people "talk about unreal things."
"The best (the government) alleges is idle, harmless talk," Gatto said.
What they discuss may be sexually deviant, but she stressed that no one was physically harmed by her client, who is the father of a 1-year-old child.
Prosecutor Hadassa Waxman contended that Valle conducted online conversations "in gruesome detail," staked out would-be victims from his police car and had taken "affirmative steps" to carry out his "operational plan."
"This is not a fantasy," Waxman said during the suspect's initial court appearance. "Each name is real."
Judge Henry Pitman sided with the prosecution, ordering Valle to remain detained pending trial. He described the allegations as "extremely disturbing" descriptions of "depraved conduct."
What made it especially troubling, the judge said, was that the suspect is a law enforcement officer and "he carried a gun."
Valle, a six-year NYPD veteran, was arrested Wednesday at his home in Queens.
He is accused of illegally accessing a national crime database to locate potential targets and scouting potential targets at their homes and workplaces.
Prosecutors also allege that Gilberto exchanged e-mails and instant messages with alleged co-conspirators about plans to target women.
Gilberto Valle's alleged plans to kidnap women so that they could be raped, tortured, killed, cooked, and cannibalized shock the conscience," Manhattan U.S. Attorney Preet Bharara said.
"This case is all the more disturbing when you consider Valle's position as a New York City police officer and his sworn duty to serve and protect. Our investigation is ongoing."
According to a law enforcement source, Valle -- who the source says has a clean record -- apparently discussed the plans with other men on a website for people who fantasize about cannibalism.
Authorities have no evidence he planned to carry out any of the acts he allegedly plotted with others on the online fantasy website, a law enforcement source says.
The NYPD has suspended him without pay, a department spokeswoman said Thursday.
A criminal complaint filed in federal court says Valle was in contact with at least two women mentioned in his plans, though FBI spokesman J. Peter Donald told CNN the agency has "no information to believe Mr. Valle harmed anyone at this time."