A US jury sentenced Dzhokhar Tsarnaev to death for his role in the April 2013 Boston Marathon bombings that killed three people and injured 264.
The panel of seven women and five men deliberated for 15 hours to reach death verdict over life in prison.
Tsarnaev (21) will be executed with a lethal injection, according to federal jury’s decision.
The same jury last month convicted Tsarnaev of killing three people and injuring almost 300 people in one of the highest-profile attacks on US soil since Sept. 11, 2001.
Reaching to death sentence, the jury heard from about 150 witnesses, including the victims of the attacks over 10 weeks of trial.
Tsarnaev was convicted of murdering 8-year-old Martin Richard, 23-year-old Chinese graduate student Lingzi Lu, 29-year-old restaurant manager Krystle Campbell and Massachusetts Institute of Technology policeman Sean Collier.
Citing a note that Tsarnaev wrote while hiding in a boat, bleeding, after a gunfight with police four days after the April 15, 2013, attack, Assistant US Attorney Steven Mellin said the ethnic Chechen had turned against his adopted country.
Defence lawyers contend that Tsarnaev was an adrift teenager under the spell of his 26-year-old brother, Tamerlan, who they claimed was mainly responsible for the bombing and murder of a police officer three days after.
They also noted that when Dzhokhar's parents returned to their hometown Russia in 2012, he was left under the influence of Tamerlan, who had become obsessed with becoming a militant.
The decision does not mean Tsarnaev will be imminently executed though, as the defence attorneys are expected to appeal the decision.