Crusius asked the court for a rearraignment hearing after federal prosecutors agreed to take the death penalty off the table.
"Defendant notifies the Court of his intention to enter a plea of guilty to the pending Indictment," the filing said.
Federal prosecutors investigated the shooting as both domestic terrorism and a hate crime because Crusius allegedly targeted Hispanics.
He allegedly told investigators he chose the store near the U.S.-Mexico border because it was frequented by Hispanic shoppers.
Crusius was indicted on 90 charges by federal prosecutors in 2019, including 22 counts of committing a hate crime resulting in death, 22 counts of use of a firearm to commit murder, 23 counts of a hate crime involving an attempt to kill and 23 counts of use of a firearm during a crime. While 22 people died on the day of the shooting or in the next two days, a 23rd person died eight months later.
There were also 23 people injured in the attack.
The 21-year-old Crusius allegedly cased the Walmart unarmed before re-entering with protective ear muffs, safety glasses and an AR-15-style assault rifle. He opened fire indiscriminately even before walking into the store.
Investigators believe Crusius posted a four-page racist, anti-immigrant document on the website 8chan before launching the attack, officials said.
ABC News' Bill Hutchinson and Luke Barr contributed to this report.