Kelley Mack Cause Of Death: What Is The Walking Dead Actress' Rare Cancer, Glioma?

Actress Kelley Mack, best known for her role as Addy in The Walking Dead, died on 2 August 2025 in Cincinnati, Ohio. She passed away at the age of 33 after months of undergoing treatment for glioma, a rare and aggressive form of brain cancer.

Her family confirmed the cause of death in a public statement, revealing that she died peacefully with her mother and aunt at her side. Mack had announced her diagnosis in late 2024, sharing her journey publicly through social media.

Who Was Kelley Mack?

Kelley Mack was best known for her portrayal of Addy in The Walking Dead Season 9. The American actress, born and raised in Ohio, also appeared in Chicago Med, 9-1-1, and the psychological thriller Broadcast Signal Intrusion. Her final film, Universal, was released in June 2025, just weeks before her death.

In addition to her acting roles, Mack was active as a voice-over artist and producer. Her career reflected a wide range of talents, from drama to horror and indie productions. Fans remember her as a rising figure in the television and film industry with a promising future.

Cancer Diagnosis and Timeline

In September 2024, Mack publicly disclosed via Instagram that she had been diagnosed with glioma, specifically a form known as diffuse midline glioma. The post included her thoughts on facing the diagnosis, as well as her commitment to undergoing treatment.

Her family revealed that she had spent her final months in Cincinnati undergoing care, and passed away on 2 August with her mother and aunt by her side. The announcement of her death was met with an outpouring of tributes from fans, industry peers, and castmates.

What Is Glioma?

Glioma is a type of tumour that originates in the glial cells of the brain or spinal cord. These cells support and protect neurons. According to the National Library of Medicine, gliomas account for around 25% of the 80,000 to 90,000 primary brain tumours diagnosed annually in the United States.

Mack was diagnosed with diffuse midline glioma, one of the most aggressive and rare types of gliomas. This cancer typically affects the brainstem and spinal cord, making it particularly difficult to treat. Symptoms can include persistent headaches, neurological changes, balance issues, and cognitive decline. Though more common in children, it can also affect adults.

There is currently no known cure for diffuse midline glioma. Treatment options are limited to palliative care, radiation, and clinical trials. The prognosis is typically poor, with median survival ranging from 9 to 12 months.

Family and Public Reaction

Following her passing, Mack's family posted a statement on her official Instagram page, referring to her as a 'bright, fervent light'.

They shared that she had made her presence known after death in the form of butterflies, a symbol that has since been embraced by fans during online tributes.

A remembrance event is scheduled to be held in her honour on 16 August 2025 in Ohio. Details of the ceremony have yet to be finalised, but the gathering is expected to include family members, friends, and former colleagues.

Final Projects and Career Legacy

Mack's last on-screen performance came in Universal, a comedy-drama released on 21 June 2025. She co-starred with British actor Joe Thomas in the film, which has since received renewed attention following her death.

In addition to Universal, she recently appeared in the horror-comedy Delicate Arch, distributed by Screambox earlier this year. Her body of work continues to gain recognition as fans revisit her performances across streaming platforms and social media.

Kelley Mack's career and story have left a lasting impression on both the entertainment industry and those personally touched by her journey.