In January 2008, she was named Editor-In-Chief of More Magazine, the leading lifestyle magazine for women over forty with a readership of 1.5 million and Editor-in-Chief and Social Media director of More.com. In July of 2015, Seymour created history by having the First Lady of the United States, Michelle Obama, guest edit an entire issue—leading to 8.5 billion media impressions. In 2008, Seymour led More to its first National Magazine Award nomination. In 2012, Seymour was named Executive Director of Meredith’s Beauty Center of Excellence; in 2009 she was named number four on the 2009 Most Powerful Fashion Editors List by Forbes magazine.
Before taking over More, Seymour served as the Editor-in-Chief for Marie Claire magazine, Redbook magazine, and teen book YM. She was Beauty Director of Glamour, and senior editor at Vogue. She is the author of two books: On the Edge, 100 Years of Vogue and I Wish My Parents Understood. In 2013 she was named Chair of the Editorial Advisory Board for Duke Magazine and a Global Ambassador for Vital Voices. She is a trustee at Dana Hall School in Wellesley, Massachusetts.