She also tweeted the news on Friday night, calling her mother "the light of my life". Three years before marrying the former Nancy Barbato, he had landed a 15-minute radio show on local station WAAT.
Nancy is survived by her two daughters, Nancy and Tina; her son, Frank Sinatra Jr., passed away in 2016 at the age of 72.
Mrs. Sinatra (nee Barbato) and the singer had been teenage sweethearts.
My mother passed away at 6:02pm tonight.
Frank Sinatra married actress Ava Gardner just weeks after divorcing Nancy.
The marriage came just as Frank Sinatra's singing career was starting to take off. "Godspeed, Momma. Thank you for everything".
They began their marriage living in a modest apartment in Jersey City, where their two eldest children, Nancy Sinatra Jr. and Frank Sinatra Jr., were born.
After Sinatra became a pop-music sensation in the 1940s, the couple moved to Los Angeles, where the singer would also become a movie star, raconteur and notorious womanizer. She had three children with him before they divorced in 1951, but remained friendly with him for years, dining together as a family and talking on the phone until the singer's death in 1998.
Nancy lived her life relatively out of the spotlight after her split from Frank, devoting herself to her family and friends.
It was there that Nancy (best known for her hit song, "These Boots Are Made For Walkin") and Frank Jr. were born.
After he divorced Gardner, Sinatra went on to marry Mia Farrow and then Barbara Marx.
Her daughter, Nancy Sinatra Jr., confirmed the news on social media.
Gay Talese, in 1966, wrote there was "no bitterness", and instead, only "great respect and affection" between Frank and Nancy.