"After consideration of the relevant facts, the applicable regulations and the submissions made by the defendant's counsel, I have determined that the United States will seek the death penalty in this matter," Holder said in a statement. "The nature of the conduct at issue and the resultant harm compel this decision."
U.S. District Judge George O'Toole in Boston had imposed a Friday deadline in the case against Tsarnaev, accused of setting off two pressure-cooker bombs near the finish line of the mass-participation marathon.
O'Toole said he wanted the trial to get rolling, the Boston Herald reported. O'Toole ordered a Feb. 12 conference with lawyers to decide the trial's starting date.
The April 15, 2013, bombings -- which exploded about 13 seconds and 210 yards apart -- killed Krystle Campbell, 29, Lingzi Lu, 23, and Martin Richard, 8, and injured an estimated 264 others in the deadliest attack on U.S. soil since Sept. 11, 2001.
A Massachusetts Institute of Technology police officer was killed in a manhunt for Tsarnaev, 19 at the time, and older brother Tamerlan Tsarnaev, 26, who was killed in a police shootout.
Dzhokhar Tsarnaev -- a Chechnya native and former University of Massachusetts-Dartmouth student who became a naturalized U.S. citizen Sept. 11, 2012 -- was later caught hiding inside a boat in a Boston suburb.
A federal grand jury in June returned a 30-count indictment against Tsarnaev. The indictment included 17 charges that could carry the death penalty, the New York Times said.
Tsarnaev pleaded not guilty to all counts in July and remains in federal custody.
Holder received a recommendation in November from U.S. Attorney Carmen Ortiz in Boston on whether to seek the death penalty. Her office is prosecuting the case.
Such recommendations typically include defense arguments on why the death penalty would be inappropriate.
Ortiz said her office would not comment on how the decision was made "other than to say that it entailed a careful and detailed consideration of the particular facts and circumstances of this case," the Boston Globe reported Thursday.
"While I understand the public interest in this matter, we have rules that limit the release of information and the scope of public statements," Ortiz said.
Justice Department protocols call on Holder to consider the strength of the evidence against Tsarnaev, the role he allegedly played in the bombing, any earlier criminal record, whether Tsarnaev would be willing "to plead guilty and accept a life or near-life sentence without the possibility of release" and the views of victims' families.
A memo to federal prosecutors outlining the protocols can be found at tinyurl.com/UPI-Death-penalty-protocols.
Since the federal death penalty was reinstated in 1988, attorneys general have authorized it for about 500 defendants.
Of those 500, three have been executed.
Seventy percent of Americans favor the death penalty for Tsarnaev, a nationwide Washington Post-ABC News poll published May 1 indicated.
A Boston Globe poll published Sept. 16 found 33 percent of people in Massachusetts supported the death penalty for Tsarnaev while 57 percent favored a life sentence without the possibility of parole.