It happened at a home on Morgan Drive near Stonehill Drive just south of U.S. Highway 64. The area is east of Zebulon - near the Wake County line.
Franklin County Sheriff's Office Chief of Staff Terry Wright said 18-year-old Oliver Funez called 911 himself around 12:45 p.m. Monday and was still on the scene when deputies arrived.
After calling 911, the 18-year-old suspect walked out of the house holding his mother's head in one hand and a knife in the other, according to authorities.
The teen - who was taken into custody without incident - is charged with first-degree murder.
Deputies said the dead woman is 35-year-old Yesenia Funez Beatriz Machado. Two young girls found in the home were unharmed.
Analysis of the crime scene was delayed by a couple hours because sheriff's deputies had to go to a neighboring county to get a search warrant. Sheriff Kent Winstead said a judge signed the order around 4:15 in the afternoon.
"We'll be here as long as it takes to do a thorough search. We owe it to the victims to make sure it's done in a proper manner - To make sure once it gets to the courthouse, justice can be served," said Wright.