The sentence was handed down on Thursday to Sajida al-Rishawi, an Iraqi woman who was paraded on state television confessing to her involvement in the November attacks.
"The court has decided to sentence to death by hanging for conspiracy to carry out terror acts" the head of the court said.
Rishawi, dressed in blue with a black scarf covering her head, remained impassive during the sentencing.
Defence lawyer Hussein al-Masri told AFP he would appeal. "The verdict is not final and we will appeal it within 30 days in accordance with the law."
The judge, who cannot be named under Jordanian law, also sentenced the accused on charges of illegal possession of explosives "for illicit use".
Co-accused at large
She is the only one of eight accused to appear in court since the high-profile trial opened in April.
The state prosecutor called for the death penalty for Rishawi and the seven other accused, who are either on the run or dead.
Among the deceased accused is top Al-Qaeda operative Abu Musab al-Zarqawi who was killed in a US raid in Iraq in June.
The Al-Qaeda group in Iraq headed by the Jordanian-born Zarqawi had claimed responsibility for the bombings.
The others who are still at large include five Iraqi nationals, among them a woman, and a Jordanian.
Conspiracy charges
Rishawi pleaded not guilty to the charges against her, which include conspiracy to carry out deadly terrorist attacks and membership of an illegal organisation.
Her court-appointed lawyer Hussein al-Masri tried but failed at the onset of the trial to obtain a psychological evaluation of his client, saying she had a family history of schizophrenia.
On Wednesday Mr Masri told AFP that he believed the jury had already decided the verdict. "I am not pessimistic. I did my best. Now it is up to the court," he said.
Rishawi was arrested four days after the bombings, during which her husband Ali Hussein al-Shammari, and two other Iraqis, blew themselves up.
Televised confession
In the dramatic television confession after her arrest, Rishawi said that she too had tried but failed to activate her explosives belt alongside her husband at the Radisson SAS hotel as a wedding reception was in full swing.
"Jordanians expect your court to do them justice... with the sentence they deserve which is death," the prosecutor told the state security court in July.
"The accused voluntarily wanted to kill innocent people in civilian areas where there were many people who felt secure, with the aim of sowing terror," he said.
Groom’s anger
In May, the groom whose wedding was devastated at the Radisson SAS, one of the three hotels bombed, demanded that Rishawi be hanged.
"I plead with the court... to carry out the maximum penalty, death by hanging in public," said Ashraf al-Akhrass, who lost his father, his father-in-law and mother-in-law in the attacks.
On one occasion she told the court that her confessions were made under duress and once she claimed to have been tortured, only to retract her statement minutes later and say investigators shouted at her.