He was convicted April 8 of all 30 federal charges against him, 17 of which carried the death penalty.
The jury of five men and seven women sentenced Tsarnaev on six of those counts, each related to bombing a public place.
Tsarnaev is expected to be sent to a federal prison in Terre Haute, Indiana, to await being put to death by lethal injection.
He has a right, however, to begin an appeals process that could take years to resolve.
The attack was conducted with a pair of homemade bombs using pressure cookers and took place a short distance from the finish line of the Boston Marathon, one of the world’s most prestigious road races.
It was the deadliest act of terrorism on U.S. soil since the terror attacks of Sept. 11, 2001.
Attorney General Loretta Lynch described the jury`s decision as a "fitting punishment" for Tsarnaev.
"We know all too well that no verdict can heal the souls of those who lost loved ones, nor the minds and bodies of those who suffered life-changing injuries from this cowardly attack", Lynch said in a statement.
"But the ultimate penalty is a fitting punishment for this horrific crime and we hope that the completion of this prosecution will bring some measure of closure to the victims and their families", she added.
Tsarnaev carried out the attack with his brother, Tamerlan, who was killed during a shootout with police four days after the bombing.
The brothers, ethnic Chechens, migrated to the U.S. from Russia more than a decade ago.
One of the survivors of the blast, Sydney Corcoran, reacted to the verdict on social media. She was injured along with her mother, Celeste, who lost both her legs in the attack.
"My mother and I think that now he will go away and we will be able to move on. Justice. In his own words, `an eye for an eye`", she tweeted.
Adrianne Haslet-Davis, a dancer who lost her leg in the bombing, said on Twitter: "My heart is with our entire Boston community. I am thrilled with the verdict".
Massachusetts Gov. Charlie Baker said the verdict represented "some kind of closure for all of those who were affected by this tragedy".
In a statement, Boston Mayor Martin J. Walsh also said he hoped the sentencing "provides a small amount of closure to the survivors, families, and all impacted by the violent and tragic events surrounding the 2013 Boston Marathon.
“Today, more than ever, we know that Boston is a city of hope, strength and resilience, that can overcome any challenge", he said.
Tsarnaev showed no visible reaction as death sentence was announced, local media reported, citing those present in the courtroom.
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