Maricopa County prosecutors said 27-year-old Douglas Ray George entered his plea Thursday. His next scheduled court date is Aug. 26.
George was arrested June 25. He's being held on suspicion of second-degree murder.
Investigators believe 23-year-old Ann Begay-Barakzai was killed at a different location than where her body was found by a passer-by on June 15.
She wasn't identified for weeks and authorities said an autopsy determined Begay-Barakzai died from blunt-force trauma.
Police say George and Begay-Barakzai lived together in Tempe and he was arrested earlier in June for domestic violence assault on his girlfriend.