The senator said in a release her mother was surrounded by family when she passed away at her home in St. Louis.
"For some time, mom's health has not been good, and our family takes comfort that she is now at rest," McCaskill said. "People all over the state have asked about her, and their prayers and concern have been greatly appreciated.
"Mom never met a stranger and lived life with enthusiasm that none of us could match. We were incredibly lucky to have a mother like her, a woman of great intellect and strength, who loved and nurtured, challenged and pushed, and was always there with wise counsel and great humor. While we know she's finally at peace, our family and her friends will all miss her so very much. Her death creates a hole in my life that will never be filled."
Betty Anne McCaskill died eight days before Election Day, when her daughter faces re-election.
The elder McCaskill was active in helping her daughter's political career but was a politician in her own right. She was the first woman ever elected to the Columbia City Council. She was inspired to get involved in politics after President Harry Truman delivered the commencement address at her University of Missouri graduation in 1950, her daughter said.