Tsarnaev and his older brother, Tamerlan, set off bombs at the finish line of the April 2013 race. The brothers were also responsible for the shooting death of an MIT campus police officer. Tamerlan later died after a shootout with police.
Read MoreTsarnaev sentenced to death for Boston Marathon bombing
The formal hearing gave victims and their families an opportunity to address Tsarnaev. Some people gathered expressed rage and grief earlier in the day.
"The choices you made are despicable," said Patricia Campbell, whose daughter, Krystle, was killed at the Boston Marathon.
"I will never have a complete family again," said Jennifer Rogers, the sister of the MIT police officer, Sean Collier.
Karen McWatters, a friend of Campbell's, looked at Tsarnaev and said, "You will die in prison alone."
Bill Richard, the father of 8-year-old Martin Richard, who was killed in the attack, also addressed Tsarnaev.
"We chose love, we chose kindness, we chose peace," he said. "That is what makes us different from him."
Marathon victims described lost limbs, broken lives and mental anguish that endured long after their surgeries were over.
—NBC News contributed to this report.