The US Circuit First Court of Appeals decided to overturn his death sentence in five points and said the judge made several mistakes.
Convictions in three cases in which Tsarnaev was convicted were overturned, the three-member jury said.
But Tsarnaev does not leave the federal prison.
“And to be very clear: Because we confirm the convictions (with the exception of the three convictions under Section 924 (c)) and the many life sentences that have been imposed on these remaining counts (which Dzhokhar has not contested), Dzhokhar will the rest of his life will remain in jail with the only question of whether the government will end his life by execution, “said Circuit Court judge Ojetta Rogeriee Thompson said.
The court ruled that Tsarnaev should receive new criminal proceedings.
The surveillance video showed the brothers carrying the pressure cooker bombs in backpacks and moving through the crowd near the marathon finish line, which the federal prosecutor described as a coordinated attack.
Tamerlan detonated the first bomb, a 6-liter pressure cooker containing gunpowder, nails, and BBs, the prosecutors said. The bomb killed Campbell, a 29-year-old restaurant manager, and permanently injured several other people who had lost their legs.
The second pressure cooker bomb carried by Dzhokhar went off 12 seconds later and killed two people, Martin and Lu, a doctoral student from China.
The bombings triggered a search for days that closed the city. During the escape, the brothers killed policeman Sean Collier from the Massachusetts Institute of Technology. After stealing an off-road vehicle, the two were followed by the police.
Tamerlan died in an explosive gun battle with the police in nearby Watertown. Dzhokhar was arrested a day later.
CNN’s Mark Morales and Steve Almasy contributed to this report.