Court documents showed Baldwin, 65, entered his plea as he waived his right to an arraignment nearly two weeks after a grand jury indicted the actor on January 19, reviving a criminal case that had been dismissed months earlier.
The Emmy-winning performer, who starred in the hit NBC television comedy 30 Rock, was allowed to remain free without posting bond under the arraignment waiver filed with the First Judicial District Court in Santa Fe.
The case, which has sparked debate about firearms safety in the production of movies and television, has little or no precedent as an instance of a Hollywood star facing criminal prosecution for an on-set fatal shooting.
Baldwin has denied responsibility for Hutchins' death in New Mexico, insisting he was told the gun was "cold," meaning it contained only blank rounds, and that the weapon fired without him pulling the trigger.
The original charges were dropped over questions of whether the reproduction Colt .45 revolver Baldwin was rehearsing with could have been modified to allow the gun to go off by itself.
Prosecutors said they sought the grand jury indictment after an independent forensic test found the gun would not fire unless the trigger was pulled.
The same bullet that killed Hutchins on October 21 in 2021 also wounded director Joel Souza.
Baldwin's plea came days after special prosecutor Kari Morrissey said in a court filing that photos and other evidence showed the live round was brought on set by the movie's weapons handler, Hannah Gutierrez.
According to courtroom testimony and police records, the pistol was handled by Gutierrez before it was picked up by the film's assistant director David Halls, who told Baldwin the gun was "cold."
Gutierrez faces trial on February 21 on separate involuntary manslaughter charges. Halls entered a plea deal and received a six-month suspended sentence on a charge of negligent use of a deadly weapon.
But the question of how a live round, strictly prohibited on film sets, was loaded into Baldwin's gun remains at the centre of the cases against Gutierrez and Baldwin, who also is a producer on the film.
Prosecutors said they had photos of live rounds on set as early as October 10, some 11 days before Hutchins was killed.
"The investigation conducted by the special prosecutor has developed substantial evidence that Ms Gutierrez brought the live rounds on set when she first began work on the film," Morrissey wrote in Monday's filing.
Morrissey cited images of live rounds from filming and others from photos Gutierrez took. The prosecutor said all six live rounds found on set appeared to have come from a box of dummy rounds that Gutierrez told detectives she brought onto the location.
Gutierrez's attorney Jason Bowles said prosecutors were "incorrect" in their assumptions.
"The evidence will come out at trial," he said in a statement to Reuters.
In police video, Gutierrez says the tray of rounds inside the box could easily have been swapped during production from a box that was not hers.