Kelley Mack Cause of Death Revealed: The Walking Dead Star Dies at 33 After Rare Brain Cancer Battle

Kelley Mack, beloved for her roles in The Walking Dead and Chicago Med, passed away on Saturday in her hometown of Cincinnati, Ohio, at just 33 years old. Her death was confirmed by her agent and family after a courageous battle with a rare and aggressive cancer—diffuse midline glioma (DMG), a form of glioma affecting the central nervous system.

Known off-screen as Kelley Klebenow, the actress peacefully passed surrounded by family, including her mother Kristen and aunt Karen, as revealed in a heartfelt social media tribute by her sister. The announcement, posted on Tuesday, spoke of Mack’s enduring spirit, her transformation into “a bright, fervent light,” and even shared how loved ones have seen her presence symbolized by butterflies since her passing.

What Is Kelley Mack’s Cause of Death?

Kelley Mack’s cause of death was due to diffuse midline glioma, a rare and aggressive cancer that affects the brain and spinal cord. According to her January 2025 Instagram post, the disease had already impacted her mobility due to spinal cord surgery complications—leaving her reliant on a walker and wheelchair.

Despite the diagnosis, Mack remained hopeful and resilient. “I am determined and know that this will eventually be a short chapter in my long book,” she wrote in that post, demonstrating both her positivity and strength in the face of adversity.

Why It Matters: A Rare Cancer That Primarily Affects Children

Diffuse midline glioma (DMG) is an especially devastating diagnosis, often affecting children between ages 5 and 10. Its presence in adults is rare, and treatment options remain limited. As per Mayo Clinic’s publicly available research, DMG is fast-growing and deeply embedded within the brain or spinal cord, making surgical removal nearly impossible.

Mack’s willingness to publicly share her diagnosis raised awareness about a condition few adults face, potentially aiding others experiencing similar health challenges.

A Look Back at Kelley Mack’s Career and Legacy

Mack first caught national attention with her portrayal of Addy in Season 9 of The Walking Dead, where her performance was praised for its emotional depth and subtle strength. She also had a memorable guest appearance as Penelope Jacobs on Chicago Med, and starred in indie projects like Mr. Manhattan, Broadcast Signal Intrusion, and Delicate Arch.

Her colleagues in the entertainment industry shared their grief and admiration across social media:

• Alanna Masterson (The Walking Dead): “What an incredible human. So proud to have fought alongside her in our final episode together.”

• Michael E. Satrazemis (Director, The Walking Dead): “A bright light on every level. All my love to those who love her.”

• Gustavo Gomez: “Your bright light will always shine on.”

These tributes reflect not only her talent but her lasting impact on cast, crew, and fans alike.

What’s Next: Remembering Kelley Mack

A remembrance service for Kelley Mack is scheduled to be held on August 16 in Ohio, as her family prepares to honor her life and legacy. Her sister emphasized the deep emotional strength Mack carried in her final moments, stating, “She made the leap to be reunited with God. I’m so f***ing proud of her.”

This celebration of her life will be attended by close family, friends, and fans who were touched by her warmth, courage, and artistry.

Kelley Mack cause of death is not just a moment of mourning in the entertainment world—it serves as a somber reminder of life’s fragility, and the battles that some face quietly, yet bravely.

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You Must Know:

What type of cancer did Kelley Mack have?
Kelley Mack was diagnosed with diffuse midline glioma (DMG), a rare and aggressive form of brain and spinal cord cancer, more commonly found in children.

How did Kelley Mack die?
She died peacefully at age 33 due to complications from glioma of the central nervous system, as confirmed by her agent and family members.

Who was with Kelley Mack at the time of her death?
Her mother Kristen and aunt Karen were by her side when she passed away in her hometown of Cincinnati, Ohio.

What roles was Kelley Mack known for?
She gained recognition as Addy in The Walking Dead and Penelope Jacobs in Chicago Med, in addition to roles in indie films.

When is Kelley Mack’s memorial service?
A remembrance for Kelley Mack will be held on August 16 in Ohio, as confirmed by her sister on Instagram.