She had been ill for months and died comfortably surrounded by her family and friends at home, a director of one of her charitable foundations said.
In the years since, Mr Thoresen said, more than 20,000 children have been treated at the centre in the desert city of Rancho Mirage and hundreds of thousands more throughout the world through videos it provides. The center was founded by Barbara and Frank Sinatra in 1986, and was established to aid "abused, neglected, and at risk children". She helped found the Barbara Sinatra Children's Center in the 1980's to assist young victims of physical and sexual abuse.
Barbara married Frank in 1976 and remained his wife for almost 22 years - the longest of his 4 marriages.
She is survived by her son from a previous Robert Oliver Marx, his wife Hillary Roberts and her granddaughter Carina Blakeley Marx.
Frank Sinatra had previously been married to Nancy Sinatra, mother of their children Nancy and Frank Jr, as well as actresses Ava Gardner, who died in 1990, and Mia Farrow.
Barbara and Frank did not have any children together.
"A very wise French lady once said to me: 'You never worry about old flames".
Sinatra remained actively involved in the facility which bore her name.