The jury considered 30 counts, 17 of which carry the death penalty. A guilty verdict has been read for all thirty counts.
The verdict was expected to be announced about 1:45 p.m but was delayed until around 2:10.
The jury of seven women and five men began their second day of deliberations Wednesday morning after Judge George O'Toole Jr. answered two questions they asked about the conspiracies Tsarnaev was charged with and the concept of "aiding and abetting."
Tsarnaev's lawyer admitted he participated in the 2013 attack but said his now-dead brother, Tamerlan, was the mastermind.
Three people were killed and more than 260 were injured when twin pressure-cooker bombs exploded near the marathon finish line in April 2013.
This is the first phase of Tsarnaev's federal death penalty trial. In the second phase, the same jury will determine if Tsarnaev will be sentenced to death or life in prison.
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The Associated Press contributed to this report.