The Minnesota lawmaker told the St. Paul CBS affiliate that he "was very well aware of" the classified government programs that gathered personal data on telephone and Internet users.
Franken also defended the program as striking the right balance between national security and the right to privacy, echoing recent assurances from the White House.
“There are certain things that are appropriate for me to know that is not appropriate for the bad guys to know,” Franken said.
The senator also said it was appropriate for the Justice Department to investigate Edward Snowden, the 29-year-old defense contractor who has claimed responsibility for the leak.
Franken's defense of the NSA programs comes despite him signing on as a co-sponsor to legislation proposed by Sens. Jeff Merkley (D-Ore.) and Ron Wyden (D-Ore.) that would require Attorney General Eric Holder to declassify opinions of the Foreign Intelligence Surveillance Act (FISA) courts.
In a release announcing the legislative efforts, the senators argue declassifying the opinions would keep the American public better informed of potential intrusions into their privacy.
A spokeswoman for Franken subsequently noted that the senator voted against the Patriot Act reauthorization in 2011 over similar concerns that the final version didn't include adequate transparency or privacy protections.
"Sen. Franken voted against reauthorizing the FISA Act because of the lack of transparency after he cosponsored and voted for three separate amendments that would have improved the bill on transparency and privacy," Franken press aide Alexandra Fetissoff said.
In the interview on Tuesday, Franken says he does think the government programs should be more open, even if there was a reason for some government secrets.
“I don't believe that the American people should have to take the government's word for it," Franken said. "I think there should be enough transparency so that the American people understand what's happening.”
The White House has defended the surveillance programs as appropriately balancing both national security and privacy interests.
"As you heard the president say on Friday, he believes that we must strike a balance between our security interests and our desire for privacy. He made clear that you cannot have 100 percent security and 100 percent privacy. And, thus, we need to find that balance," White House press secretary Jay Carney said Tuesday.
This post was updated at 5:57 p.m.