Katherine Russell, aged 24, who married Tsarnaev in June 2010 and has a 3-year-old child with him, is "doing everything she can to assist [the] ongoing investigation", her attorneys said in a media statement.
Tsarnaev, aged 26, and his 19-year-old brother Dzhokhar - who is currently hospitalised and facing terror charges - are accused of having carried out the 15 April twin bombing at the Boston Marathon that killed three people and wounded more than 260.
The statement said news that the two brothers may have been behind last week's carnage came as an "absolute shock" to Russell and her family.
"As a mother, a sister, a daughter, a wife, Katie deeply mourns the pain and loss to innocent victims, students, law enforcement, families and our community," it said.
"In the aftermath of this tragedy, she, her daughter and her family are trying to come to terms with these events."
Tamerlan, the older of the two ethnic Chechen brothers, who had been living in the United States for over a decade, reportedly embraced a more radical form of Islam in recent years and seems to have been the ringleader of the attack.
The FBI questioned Tamerlan in 2011 following a request from Moscow, and is now scrutinising a six-month-long trip he made to the troubled Russian regions of Dagestan and Chechnya in 2012.
Both predominantly Muslim regions are home to fierce Islamist and separatist groups. One of the most prominent Islamist groups has denied any involvement in the Boston attacks, saying it is only at war with Russia.