Frances Adeline Seward (née Miller) was born on September 24, 1805 in Cayuga County, New York to Judge Elijah Miller and Hannah Miller (née Foote). She was the younger of two daughters. Her older sister was Lazette Maria Worden (née Miller). When Frances was five years old, her mother died. Her childhood home consisted of Judge Miller, Lazette, her paternal aunt, Clarinda McClallen (née Miller), and her paternal grandmother, Paulina Miller (née Titus). Frances was raised as a Quaker.  

Frances attended the Troy Female Seminary with her sister. In 1821, she met William Henry Seward (he went by Henry in close circles) through her classmate and his sister, Louisa Cornelia Canfield (née Seward). Her father in 1823 employed Henry. On October 20, 1824, Frances and Henry wedded. They had five children together, Augustus Henry Seward, Frederick William Seward, William Henry Seward Jr., Cornelia Seward (who died in infancy), and Frances Adeline Seward.

On April 14, 1865, Henry and Frederick were severely injured by Lewis Powell in the same coordinated attack that killed Abraham Lincoln. Frances immediately went to Washington D.C. to care for her family. On June 21, 1865, Frances died in Washington D.C and is buried next to her husband in Fort Hill Cemetery in Auburn, New York.