The Casey family released a statement saying she died peacefully at Regional Hospital in Scranton on Friday. She passed after battling a brief illness.
The family did not state her cause of death.
"We are grateful to Ellen for her dedication to the people of Pennsylvania. May her memory be a blessing for her family and all of us who benefited from her service," First Lady Lori Shapiro said in a statement.
Casey served alongside her husband, Governor Bob Casey Sr., between 1987 and 1995.
She was also the mother of current U.S. Senator Bob Casey Jr.
Governor Josh Shapiro has ordered flags to be lowered to half-staff in her honor.