‘The Walking Dead’ Actress Kelley Mack Dies at 33 After Cancer Battle

Cincinnati, Ohio — Kelley Mack, known for playing Addy in The Walking Dead Season 9, died peacefully on August 2, 2025, in Cincinnati at age 33. She succumbed to diffuse midline glioma, a rare and aggressive form of brain and spinal cancer, diagnosed in 2024. Her family announced her passing on August 5 via Instagram, stating, “Such a bright, fervent light has transitioned to the beyond.”

In September 2024, Kelley Mack began experiencing persistent lower back pain, initially assumed to be a slipped disc, alongside a neuropathic "itching" sensation in her right thigh. Over time, she had shooting pains in her legs and back and couldn’t lie flat, often needing a recliner to sleep. An urgent MRI revealed a spinal cord mass; a biopsy in January confirmed it was diffuse midline glioma (DMG).

Diffuse midline glioma is classified as a grade IV malignant tumor, known for its rapid progression and resistance to treatment, particularly when located in the spinal cord or brainstem.

In the U.S., gliomas are rare, with only about six cases per 100,000 people annually, yet remain the most common primary tumors of the brain and spinal cord.

Mack underwent surgery that resulted in the loss of most movement in her legs; she required a walker and wheelchair. She then began radiation therapy in Cincinnati and publicly shared her recovery journey—including relearning to climb stairs by March 2025.

Symptoms of DMG may include persistent back pain, neurological deficits, balance issues, vision changes, and swallowing difficulties. Diagnosis is often delayed due to the subtle onset of symptoms, and there is currently no known prevention, though research points to genetic mutations as possible factors.

Prognosis remains poor—only about 10 % of patients survive beyond two years post‑diagnosis, highlighting the urgency for earlier recognition and research.

In one of her final Instagram posts, she wrote about maintaining optimism despite her prognosis, saying, “I still feel like the luckiest person in the world to be alive.” She also used her platform to raise awareness about the underfunding of research for rare cancers like glioma.

Born Kelley Lynne Klebenow on July 10, 1992, Kelley Mack’s storytelling passion began with a childhood video camera gift. She earned 35 acting credits, including roles in Chicago Med as Penelope Jacobs, 9-1-1, and films like Broadcast Signal Intrusion and Delicate Arch. She provided the voice match for Gwen Stacy in Spider-Man: Into the Spider-Verse and appeared in a Rakuten ad with her mother, Kristen.

She was also remembered fondly by fans and colleagues for her performance as Addy, a member of the “Highwaymen” group in The Walking Dead, a role that brought her widespread recognition in 2019.

As a producer, she co-wrote On The Black, winning a Jury Choice Award at the Atlanta Horror Film Festival.

Personal Life and Legacy

Kelley Mack graduated from Chapman University in 2014 with a cinematography degree. Based in Los Angeles for 11 years, she loved hiking, biking, and playing piano.

Her family described her as “brilliant, selfless, compassionate, funny, and fiercely loyal.”

She is survived by parents Kristen and Lindsay, siblings Kathryn and Parker, grandparents Lois and Larry, and boyfriend Logan. Mack will appear posthumously in Universal.

She requested her body be donated to brain cancer research following her death.

Memorials are planned for August 16 in Ohio and another in Los Angeles.

(Rh/Eth/MKB/MSM/SE)