Messner's battle started in 1996 with colon cancer that more recently spread to her lungs. She updated her fans by posting letters on her site, detailing her chemotherapy and condition.
She died peacefully at her home Friday, said her booking agent, Joe Spotts, in an e-mail.
A family service was held Saturday in a private cemetery, where her ashes were interred, he said. A public ceremony may be in the works, reports CBS News correspondent Drew Levinson.
Messner made her final television appearance on CNN's "Larry King Live" just days before she died, reports Levinson. During that last interview, she said goodbye to her friends, loved ones and fans.
"I genuinely love you. I genuinely care. And I genuinely want to see you in heaven someday," she said on the show.
She had frequently spoken about her medical problems, saying she hoped to be an inspiration to others. "Don't let fear rule your life," she said. "Live one day at a time, and never be afraid." But she told well-wishers in a note on her Web site in May that the doctors had stopped trying to treat the cancer.
In an interview with CNN's Larry King two months later, an emaciated Messner — still using her trademark makeup — said, "I believe when I leave this earth, because I love the Lord, I'm going straight to heaven." Asked if she had any regrets, Messner said: "I don't think about it, Larry, because it's a waste of good brain space."
Born Tammy Faye LaValley, she married Jim Bakker in 1961 and the two of them started on the gospel circuit. Within a few years, they hit it big, eventually reaching 13 million viewers with their PTL network.
The letters stood for "Praise the Lord" or "People that Love."
For many, the TV image of then-Mrs. Bakker forgiving husband Jim's infidelities, tears streaking her cheeks with mascara, became a symbol for the wages of greed and hypocrisy in 1980s America.
She divorced her husband of 30 years, with whom she had two children, in 1992 while he was in prison for defrauding millions from followers of their PTL television ministries.
"She is now in Heaven with her mother and grandmother and Jesus Christ, the one who she loves and has served from childbirth," he said. "That is the comfort I can give to all who loved her."
Messner's second husband also served time in prison. She married Roe Messner, who had been the chief builder of the Bakkers' Heritage USA Christian theme park near Fort Mill, S.C., in 1993. In 1995, he was convicted of bankruptcy fraud, and he spent about two years in prison.
Through it all, Messner kept plugging her faith and herself. She did concerts, a short-lived secular TV talk show and an inspirational videotape. In 2004, she cooperated in the making of a documentary about her struggle with cancer, called "Tammy Faye: Death Defying."
"I wanted to help people ... maybe show the inside (of the experience) and make it a little less frightening," she said.
That same year, she appeared on the WB reality show "The Surreal Life," co-starring with rapper Vanilla Ice, ex-porn star Ron Jeremy and others. She told King in 2004 that she didn't know who Jeremy was when they met and they became friends.
Messner was never charged with a crime in connection with the Bakker scandal. She said she counted the costs in other ways.
"I know what it's like to hit rock bottom," she said in promotional material for her 1996 video "You Can Make It."
In the mid-1980s, the Bakkers were on top, ruling over a ministry that claimed 500,000 followers. Their "Jim and Tammy Show," part TV talk show, part evangelism meeting, was seen across the country. Heritage USA boasted a 500-room hotel, shopping mall, convention center, water-amusement park, TV studio and several real-estate developments. PTL employed about 2,000 people.
Then in March 1987, Bakker resigned, admitting he had a tryst with Jessica Hahn, a 32-year-old former church secretary.
Tammy Faye Bakker stuck with her disgraced husband through five stormy years of tabloid headlines as the ministry unraveled.