The victims
Victims' profiles in full
A police officer was killed in the days following the attack as Tsarnaev and his brother, who also died, attempted to flee.
As the guilty verdicts were read on Wednesday, Tsarnaev kept his hands folded in front of him and looked down .
Nearby, the mother of one victim, eight-year-old Martin Richard, wiped tears from her face after the verdict was read.
Richard's father embraced one of the prosecutors.
The governor of Massachusetts welcomed the verdict, and Boston Mayor Martin Walsh said: "I hope today's verdict provides a small amount of closure".
The family of Officer Sean Collier, who was killed days after the attack, said: "While today's verdict can never bring Sean back, we are thankful that Dzhokhar Tsarnaev will be held accountable for the evil that he brought to so many families."
Tsarnaev's defence team say he took part in the bombing, but argue that his elder brother, Tamerlan, was the mastermind of the attack who influenced Tsarnaev into participating.
Prosecutors portrayed the brothers as equal partners in a plan to "punish America" for wars in Muslim countries.
Among the most damning evidence was a video that showed Tsarnaev placing a backpack bomb near to Martin Richard, and a statement scrawled inside the boat where he was found hiding days after the attack.
At the scene: Tara McKelvey
A court official warned against emotional outbursts as the verdict was read.
"There is to be no reactions," he told people in the room. "Maintain complete silence."
People on the government's side, near the FBI agents and the Watertown, Massachusetts, police chief, had cried as they watched videos of the bombings. Today they were quiet as the verdicts were read: "guilty, guilty, guilty".
Earlier Tsarnaev had given his lawyer, Judy Clarke, a half-fist-bump. She didn't return it.
This afternoon he was more subdued. He stood and paid close attention as the verdicts were read, occasionally rocking from side to side. He put his hands in his pockets then took them out quickly.
He has long lashes, and he blinked a lot. When he was led out of the room, he walked quickly, as before, but his step was less springy.
"Stop killing our innocent people and we will stop," he wrote, as he lay wounded and bleeding inside the dry-docked boat in suburban garden.
The jury was also shown a surveillance video of Tsarnaev casually purchasing milk at a nearby supermarket less than 30 minutes after the bombs wreaked carnage at the finish line.
Tsarnaev is an ethnic Chechen. His family moved to the US about a decade before the bombings.