Ailina Tsarnaeva, 23, is charged with impeding an investigation into the use of counterfeit money in 2010, The Boston Globe reported Wednesday.
The sister of Tamerlan and Dzhokhar Tsarnaev, she had been sought on an arrest warrant for more than two years.
Her lawyer, George Gormley, told the court Tsarnaeva, who lives in New Jersey, "is here voluntarily to get herself in good standing with the court."
He said his client did not object to checking in with the Massachusetts probation office once a week.
Tsarnaeva, who has a 1-year-old child and is expecting another, is unlikely to flee, Gormley told the judge.
Bombs allegedly placed by her brothers near the finish line of the Boston Marathon killed three people and injured more than 260. Tamerlan Tsarnaev, 26, died after he was shot by police and run over by his brother. Dzhokhar Tsarnaev, 20, was arrested later that same day and faces charges that could result in the death penalty.
She was charged in 2011 after prosecutors accused her of picking up someone who passed counterfeit money at a Boston mall in 2010. Police said Tsarnaeva acknowledged being at the mall, but refused to say who was involved.
A pretrial hearing on the charges is set for Dec. 4, but the judge said she did not have to present.