Dias Kadyrbayev and Azamat Tazhayakov were arraigned Tuesday in federal court on charges of conspiracy to obstruct justice.
Prosecutors say they tried to thwart the investigations of the deadly April explosions by throwing away fireworks and other items they found in the dorm room of Dzhokhar Tsarnaev the day before his capture.
Authorities found the fireworks in a New Bedford landfill.
Lawyers for both men have said they did nothing wrong.
Both are 19-year-olds from Kazakhstan. Like Tsarnaev, they were students at the University of Massachusetts Dartmouth.
If convicted, they face up to 20 years in prison. Family members of both attended the hearing.