Michael Nolan entered the plea in court Tuesday, the Northwest Florida Daily News reported.
Nolan was arrested June 5 for the May 2 incident in which he allegedly let his mother lie in her own feces for three days before he called for help, an Okaloosa County Sheriff's arrest report shows.
When the mother, whose name was not reported, was brought to a hospital, she was covered in feces and maggots and had "other possible parasitic-type topically on her skin," hospital records state.
The woman was also suffering from a urinary tract infection as well as "oozing" open wounds, prompting doctors to perform a blood transfusion on her, records show.
Nolan told officials he "knew that he should have acted and failed to do so, which caused serious medical and hygienic issues," his arrest report states.
He is scheduled to appear in court for a jury trial Aug. 27.