The lawsuit alleges the FBI, CIA and NYPD conspired in the activist's assassination in 1965 and engaged in a decades-long coverup that has interfered with the family's search for truth and justice.
Ilyasah Shabazz, Malcolm X's daughter, who represented her family at a New York City press conference, and her lawyers claim that they have uncovered new evidence that they believe will prove that the NYPD and FBI conspired to kill Malcolm X.
"We fought primarily for our mother, who was here," Ilyasah Shabazz said of Betty Shabazz, who died in 1997, from the site of the former Audubon Ballroom, where her father was killed. "My mother was pregnant when she came here to see her husband speak; someone who she just admired totally and to witness this horrific assassination of her husband ..."
Malcolm X was shot 21 times by multiple gunmen on Feb. 21, 1965 during a speech at the Audubon Ballroom in Washington Heights -- in front of his wife and daughters. He was 39 years old.
Civil rights attorney Ben Crump, who is representing the family, said that the lawsuit alleges authorities engaged in the decades-long cover-up that deprived Malcolm X and his family of justice.
"It is not lost on us that justice has been delayed in this matter," Crump said. "The government fingerprints are all over the assassination of Malcom X and finally, we believe we have the evidence to prove it."
In the years since, questions have escalated about the role of law enforcement in Malcolm X's death.
"Over the last three years, every day, every week, every month we have been unearthing new evidence," Crump said.
In the lawsuit, the family said the prosecution team suppressed the government's role in the assassination.
The lawsuit alleges that there was a "corrupt, unlawful, and unconstitutional" relationship between law enforcement and "ruthless killers that went unchecked for many years and was actively concealed, condoned, protected, and facilitated by government agents," leading up to the murder of Malcolm X.
According to the lawsuit, the NYPD, coordinating with federal law enforcement agencies, arrested the activist's security detail days before the assassination and intentionally removed their officers from inside the ballroom where Malcolm X was killed. Meanwhile, it adds, federal agencies had personnel, including undercover agents, in the ballroom but failed to protect him.
Three men were convicted of crimes in the death but two of them were exonerated in 2021 after investigators took a fresh look at the case and concluded some evidence was shaky and authorities had held back some information.
The family hopes the new legal action will lead them to the truth.
"We will turn over every rock, we will open up every drawer, we will look at every file to get the truth about what happened to Malcolm X," said attorney Jonathan Moore.
The law enforcement agencies have not yet responded due to the pending litigation.
(The Associated Press and ABC News contributed to this report.)