The 56-year-old actress will instead be traveling to England to be with her family as well as to attend funeral services for her mother.
"My mother survived incredible challenges... her health issues that she never complained about... three and half years in a Japanese concentration camp in World War II and the loss of her husband John who was the love of her life," Seymour said in a statement, according to People.
"However, she was always a beacon of love and hope for all she met and especially for my sisters Anne and Sally and for our entire family. Her spirit was indomitable and will continue to live forever in our hearts."
Seymour told reporters during a conference call last month that she's participating in Dancing with the Stars' fifth season because the ABC reality competition series "turned out to be my mother's favorite show ever."
"She would not miss it ever," said Seymour of her mother during the conference call.
"She got very, very excited when I said I was going to do this in her honor. I asked if she'd be proud of me, and she actually spoke. It was the only word she's spoken since the stroke. She said, 'Yes.' So I decided I'm going to do the best I can and hopefully I'll do my mother and anybody with back injuries or advanced age proud."
Whether Seymour -- assuming she isn't eliminated on tonight's Week 2 results show broadcast -- plans to continue participating in Dancing with the Stars currently remains unclear. "All of those things remain unclear at the moment," Seymour's representative told Access Hollywood when asked how Frankenberg's death would affect the star's upcoming Dancing with the Stars appearances.