The panel deliberated slightly more than two hours.
Witnesses said Hasan showed no emotion when the sentence was handed down, NBC News reported.
Hasan will be sent to the military's death row at Fort Leavenworth, Kan., but an appeal is automatic under the military justice system, the Austin (Texas) American-Statesman said. If he is executed, he will be the first service member put to death under the military justice system in more than a half-century.
The same panel of 13 Army officers, all senior to Hasan, convicted him Friday of 13 counts of premeditated murder and 32 counts of attempted premeditated murder.
The panel also ruled Hasan would lose his monthly salary of more than $7,200 a month, which he had continued to receive after the crime, as required by law.
The newspaper said he won't officially lose his rank of major until he is dismissed from the Army.
In closing arguments Wednesday morning, prosecutors asked the panel to give Hasan the death penalty.
"He is not giving his life, we are taking his life," lead prosecutor Col. Michael Mulligan said. "This is not his gift to God; this is his debt to society. This is not a charitable act; this is the cost of his murderous rampage.
"He is not now, and he never will be, a martyr. He is criminal. He is a cold-blooded murderer."
Hasan, an Army psychiatrist acting as his own lawyer, again offered no defense or explanation of his motive in his 2009 shooting rampage at a Fort Hood soldier deployment center.
Hasan, who turns 43 Sept. 8, could become the first U.S. soldier in 52 years executed in the military's death chamber at Leavenworth. All panel members had to agree on the death penalty, and President Obama still must approve it.
Deliberations began shortly after 11 a.m., after the judge, Col. Tara Osborn, gave lengthy instructions on how to reach a punishment decision, the San Antonio Express-News reported.
Tuesday Hasan asked no questions of prosecution witnesses -- including the spouses and parents of six murder victims -- who testified about their struggles since the shooting. The struggles they spoke about included alcohol abuse, depression, suicidal thoughts and unraveled relationships.
"When a parent loses a child, it creates an irreplaceable void," said Jerri Krueger, mother of Sgt. Amy Krueger, who was 29 when Hasan killed her.
"I live with that every day," Krueger said.
No witness addressed Hasan directly or looked at him at the defense table, CNN said.
Hasan himself watched all the witnesses, occasionally wiping his nose, the network said.