Moussaoui is the only person charged in the United States in connection with the terrorist attacks on the World Trade Center and Pentagon that killed nearly 3,000 people.
The 37-year-old Frenchman sat in his chair and prayed silently as the verdict was read, according to the Associated Press.
Once the judge and jury left the room, Moussaoui shouted, “You’ll never get my blood. God curse you all,” reported Reuters.
Moussaoui faces a second phase of his sentencing trial, set to begin Thursday, to determine whether he will be put to death or spend life in prison.
Testimony will include families of 9/11 victims describing the human impact of the al-Qaida mission that flew hijacked airplanes into the World Trade Center towers, Pentagon and into the ground in Pennsylvania.
Moussaoui was in jail at the time of the attacks, but prosecutors argued he would have been able to stop the missions had he revealed his ties to the terrorist organization and its plans.
He pleaded guilty in April 2005 to conspiring with al-Qaida to hijack aircraft and other crimes, but didn’t say he was part of the 9/11 plot until he recently took the stand against his counsel’s wishes and claimed he would have flown a fifth hijacked airplane into the White House that day.
Hamilton Peterson, whose father Donald and stepmother Jean died on Flight 93 that crashed into the ground in Pennsylvania, said outside the courtroom Monday, “I am grateful to the jury for having made that decision and I feel confident in light of Moussaoui’s own testimony that it is the right decision and look forward to the next phase of the case and the final determination of execution.”