Spade is survived by her husband of more than three decades, designer Andy Spade, and their 13-year-old daughter.
The Associated Press reports the 55-year-old was found in her Park Avenue apartment with a red scarf around her neck that was attached to a nearby doorknob.
Spade, known for a popular line of handbags, sold a controlling stake in her namesake company to Neiman Marcus in 1999. Just a year ago, Coach bought the Kate Spade company in a $2.4 billion deal. Spade sold her company in 2007 and took time off to raise her daughter, She started a new accessories company in 2016 called Frances Valentine, named after her daughter.
Police confirmed the designer's death under her birth name, Katherine Noel Brosnahan.
Fans wrote of how simply owning something with Kate Spade's name on it was special. She did not show her bedroom but spoke on her love for the home and her family.
Kate Spade was sister-in-law to actor, comedian, and Saturday Night Live veteran David Spade.
Kate Spade New York issued a statement confirming the "incredibly sad news" of its founder's death.
A woman walks by the Kate Spade store in New York's Soho neighborhood, Tuesday, June 5, 2018. Many remembered getting their first Kate Spade bag. Kate will be dearly missed.
"She was a great talent who had an immeasurable impact on American fashion and the way the world viewed American accessories", the statement read. After multiple attempts to help her sister Saffo said she finally "let go", adding, "sometimes you simply can not SAVE people from themselves!"