Sanders posed "one very simple question" in a letter Friday to the agency's director, Keith Alexander.
"Has the NSA spied, or is the NSA spying, on members of Congress or other American elected officials?" the senator asked.
He specified that "spying" would include the collection of metadata (information pertaining to a phone call's time, date, length and duration), along with Internet and email history.
An NSA spokesman indicated to The Washington Post on Saturday that when it comes to that type of spying, Sanders and his colleagues are treated like everybody else.
"Members of Congress have the same privacy protections as all U.S. persons," the spokesman told the Post. "We are reviewing Sen. Sanders’s letter now, and we will continue to work to ensure that all members of Congress, including Sen. Sanders, have information about NSA’s mission, authorities, and programs to fully inform the discharge of their duties.”