Dias Kadyrbayev, 21, pleaded guilty in August 2014 to charges of conspiracy and obstruction of justice for taking and concealing evidence from Tsarnaev's dorm room.
Tsarnaev and his brother, Tamerlan, set off a pair of pressure-cooker bombs at the finish line of the April 15, 2013, marathon, killing three people and injuring more than 260 others. Three days later, Kadyrbayev saw a photo of Tsarnaev released by the FBI on television.
He texted Tsarnaev, "u saw the news?"
"Yea bro I did," Tsarnaev answered. He followed up with an ominous warning, "Better not text me my friend."
But Tsarnaev sent one more text to Kadyrbayev that led him to interfere with the investigation of the bombings, prosecutors said.
"If yu want yu can go to my room and take what's there," he typed. Tsarnaev ended the conversation with "salam aleikum," an Arabic phrase meaning, "peace be upon you."
Kadyrbayev went to Tsarnaev's dorm room at the University of Massachusetts Dartmouth. He took a laptop and a backpack containing fireworks that the brothers used to build the bombs, a thumb drive and a jar of Vaseline, prosecutors said. He threw most of the things in a trash bin and hid the laptop in his apartment.
Investigators recovered the backpack in a landfill two days later, but the contents were contaminated and damaged.
"The concealment and destruction of evidence can have profound effects on the course of an investigation," U.S. Atty. Carmen Ortiz said in a statement.
According to a Justice Department news release, Kadyrbayev will be deported to Kazakhstan after he serves six years in federal prison. He was in the U.S. on a student visa while he studied at the University of Massachusetts Dartmouth.
Tsarnaev, now 21, was convicted of the bombings and sentenced to death. His brother, Tamerlan, was killed during a shootout with police a few days after the bombings. The brothers also killed an MIT campus police officer as they tried to flee.