Epstein's passing comes two years after the loss of Kathie Lee's husband, Frank Gifford, in August 2015. Her father, Aaron Epstein, died in 2002.
Over the years, Epstein made several guest appearances alongside her beloved daughter, including Gifford's 15-year stint on Live with Regis & Kathie Lee.
The official Kathie Lee and Hoda Instagram account posted condolences, writing, "Kathie Lee's beloved mom, Joan, has died at the age of 87. Our thoughts and prayers go out to KLG and her entire family."
Gifford's Today co-anchor, Hoda Kotb, shared her condolences alongside an adorable photo of the two with their mothers.
"We will miss you sweet Joannie xoxoxo," wrote Kotb, who also tweeted her support for Gifford.
Gifford's daughter, Cassidy, also posted memories of her late grandmother to social media.
"Jesus & Pop Pop are much cooler, anyhow and I know they're both smiling now that they have you back... so until we meet again, love you to heaven, Cuddles," she captioned a photo of the two embraced in a hug.
"[She's] the sunniest person I know, except for maybe Hoda. Because who’s happier than Hoda?" Gifford said of her mother in May 2016 during a Today interview. "It can be 10 days of rain, and she'll say, 'You know, I like a rainy day. It slows you down.'"
Gifford, who would call Epstein every morning at 9 a.m. before going on air, also shared how her mother supported her and encouraged her to follow her dreams.
"I left home when I was 17 years old to pursue my career, and [my mom and dad] were all for it," she said. "They figured that they had raised me, and they wanted me to follow my passion. I've tried to do that with my own children. She gave me wings."