Tsarnaev, 21, was found guilty of all 30 counts against him, with 17 of the charges carrying the death penalty. The same US District Court jury will now decide whether to sentence him to death or life in prison without possibility of parole.
Tsarnaev silently looked down, occasionally fidgeting, as the lengthy verdict was read. The courtroom was packed with survivors of the attack, the parents of 8-year-old Martin Richard, the youngest fatality, and law enforcement officials, including former Boston Police Commissioner Ed Davis.
Jurors spent just over 11 hours evaluating Tsarnaev's guilt in two days of deliberations, following 16 days of testimony.
Defense lawyers began the trial by admitting that Tsarnaev carried out the April 15, 2013, bombing but said he did so at the bidding of his older brother Tamerlan, 26, who died following a gunfight with police in Watertown, Massachusetts.
Prosecutors laid out evidence that the defendant, an ethnic Chechen who immigrated from Russia a decade before the attack, had read and listened to jihadist materials, and wrote a note in the boat where he was found hiding suggesting the bombing was an act of retribution for US military campaigns in Muslim-dominated countries.
The blasts killed restaurant manager Krystle Campbell, 29, Chinese exchange student Lingzi Lu, 23, and Richard. Tsarnaev also was found guilty of the fatal shooting of Massachusetts of Institute of Technology police officer Sean Collier, 26.
Federal prosecutors detailed jihadi writings, including a copy of al Qaeda's "Inspire" magazine with an article on bomb-making found on of Tsarnaev's computers, describing that as evidence that he was an extremist who wanted to "punish America."
The trial, which began in early March after a two-month jury selection process, dredged up some of worst memories in living memory in Boston. The twin pressure-cooker bombs ripped through the crowd of spectators at the race's finish line, setting off a mad rush to save the hundreds of people wounded, many of whom lost legs.
Three days later, the Federal Bureau of Investigation released images of the Tsarnaev brothers, saying they were the suspected bombers and seeking information on their identities. That set the stage for 24 hours of chaos as the duo fatally shot Collier in an unsuccessful attempt to steal his gun and went on to carjack a Chinese entrepreneur before police found them in the suburb of Watertown.
The pair fought a desperate gunfight with police, throwing a smaller pressure-cooker bomb similar to the ones they used at the race, as well as smaller pipe bombs. When Tamerlan Tsarnaev ran out of bullets in the rusty Ruger handgun his brother had borrowed from a drug-dealing friend, he charged Watertown police officers who were trying to wrestle him to the ground. Dzhokhar then hopped into the carjacked Mercedes SUV and sped toward the group, running over his brother and dragging him.
