Walters told ABC's "Good Morning America" on Thursday that she interviewed Madoff for two hours at the prison in Butner, N.C., where he's serving a 150-year sentence. No cameras were allowed in the prison.
Walters said Madoff told her he thought about suicide before being sent to prison. But since he's been there, he no longer thinks about it.
His comments come ahead of his wife's appearance Sunday's episode of CBS' "60 Minutes." Ruth Madoff said in excerpts that they tried to kill themselves after he admitted stealing billions of dollars in the largest Ponzi scheme in history.
Walters quoted Madoff as saying: "I feel safer here (in prison) than outside. I have people to talk to, no decisions to make. I know I will die in prison. I lived the last 20 years of my life in fear. Now, I have no fear because I'm no longer in control."
She also said he told her he understands why his one-time clients hate him, and that the average person thinks he "robbed widows and orphans." But he also told her, "I made wealthy people wealthier."
Ruth Madoff's appearance on "60 Minutes" will be her first interview since her husband's December 2008 arrest. She says they had been receiving hate mail and "terrible phone calls" and were distraught.
"I don't know whose idea it was, but we decided to kill ourselves because it was so horrendous what was happening," she says in the interview, according to excerpts released by CBS.
She says it was Christmas Eve, which added to their depression, and she decided: "I just can't go on anymore."
She says the couple took "a bunch of pills" including the insomnia prescription medication Ambien, but they both woke up the next day. She says the decision was "very impulsive" and she's glad they didn't die.
The couple's son Andrew Madoff also will talk about his experience.
Another son, Mark Madoff, hanged himself by a dog leash last year on the anniversary of his father's arrest. Like his parents, he had swallowed a batch of sleeping pills in a failed suicide attempt 14 months earlier, according to his widow's new book, "The End of Normal: A Wife's Anguish, A Widow's New Life."
Bernie Madoff was arrested on Dec. 11, 2008, the morning after his sons notified authorities through an attorney that he had confessed to them that his investment business was a multibillion-dollar Ponzi scheme. He admitted cheating thousands of investors. He pleaded guilty to fraud charges.
Madoff, who's in his 70s, ran his scheme for at least two decades, using his investment advisory service to cheat individuals, charities, celebrities and institutional investors.
An investigation found Madoff never made any investments, instead using the money from new investors to pay returns to existing clients - and to finance a lavish lifestyle for his family. Losses have been estimated at around $20 billion, making it the biggest investment fraud in U.S. history.