A young actress known for her roles on two popular television series has died at just 33 years old, leaving behind family, friends, and fans stunned and grieving. Kelley Mack, who appeared in multiple episodes of The Walking Dead and Chicago Med, passed away Saturday after a battle with cancer.
It’s with immense sadness that we share the passing of Kelley Mack at the age of 33.
Kelley is known to fans of #TheWalkingDead for portraying the character of Addy in Season 9.
Our sincere thoughts are with her loved ones during this difficult time. pic.twitter.com/u810HeyGtX
— The Walking Dead World (@TWalkingDWorld) August 5, 2025
Her family confirmed the news in an emotional post shared Tuesday on Mack’s Instagram. According to the statement, Mack died peacefully in her hometown of Cincinnati, Ohio, with her mother and aunt by her side. She had been privately fighting glioma, a rare form of cancer that attacks the brain or spinal cord, for several years.
“It is with indelible sadness that we are announcing the passing of our dear Kelley,” her sister Kathryn wrote in the announcement. “Such a bright, fervent light has transitioned to the beyond, where we all eventually must go.”
Family members say that in the days since her passing, several loved ones have reported seeing butterflies—a symbol they believe is a sign from Kelley herself.
Mack had been open about her cancer diagnosis and the struggles that followed. In entries she wrote for the online health journal CaringBridge, she detailed how symptoms began quietly in October 2024 with persistent lower back pain. Just weeks later, that discomfort became serious enough to send her to the emergency room on Thanksgiving Day.
An MRI soon revealed something worse than she feared—an abnormal mass on her spinal cord.
In January, doctors diagnosed her with diffuse midline glioma, a rare and aggressive tumor. According to the National Cancer Institute, it often forms in the brain or along the spine, where it can interfere with movement and basic body functions.
Mack underwent a biopsy in early 2025, but the procedure resulted in partial paralysis. She later wrote, “Due to the biopsy surgery on my spinal cord, I have lost the use of my right leg and most of my left leg, so I now get around with a walker and a wheelchair.”
She stayed positive even through that difficult chapter. In a blog post from March, she joked, “Life has also had its ups and downs lately am I right,” while describing her daily efforts to re-learn how to walk.
Mack, whose full name was Kelley Lynne Klebenow, had a passion for acting from a young age. Her first film appearance came in The Elephant Garden, a student film that earned the Student Visionary Award at the Tribeca Film Festival in 2008.
But it was her role as “Addy” on The Walking Dead that gained her national attention. She played the character during season nine of the series, appearing in five episodes set in the Hilltop Colony. “I was only supposed to be in 2 episodes originally,” she said in a 2019 interview, “so I was grateful to have been able to work on five of them.”
The Walking Dead actress Kelley Mack, 33, has died following a battle with glioma of the central nervous system, a rare form of brain cancer. Her family announced her death on Instagram, stating she “passed peacefully on Saturday evening with her loving mother Kristen and… pic.twitter.com/Mwsgt3d3Bi
— True Crime Updates (@TrueCrimeUpdat) August 6, 2025
Mack’s sudden death has sparked messages of condolence from fans and colleagues. Many are remembering her not just for her acting, but for her strength and honesty during her final years.
She is survived by her parents, Kristen and Lindsay Klebenow, her sister Kathryn, brother Parker, and grandparents Lois and Larry Klebenow.
Her funeral is scheduled for August 16.
