Kelley Mack, the talented actress known for her roles in Chicago Med, 9-1-1, and The Walking Dead, has tragically passed away at the young age of 33. Her demise on Saturday, 2 August 2025, was caused by a rare glioma of the central nervous system, a type of brain cancer.

Mack's agent, Julie Smith, confirmed the news on 5 August 2025. Her sister, Kathryn Klebenow, also shared the heartbreaking news on Instagram, stating that Kelley passed peacefully in her hometown of Cincinnati. Kathryn noted that Kelley was "extremely brave" and transitioned "with her loving mother Kristen and steadfast aunt Karen present".

A glioma is a tumour formed when glial cells, which support neurons in the nervous system, grow out of control. These tumours usually originate in the brain. Mack had completed proton radiation treatment in April 2025. The Mack family has announced plans for a recognition and remembrance of Kelley's life in Glendale, Ohio, on 16 August 2025. A further celebration of life is scheduled for an unspecified date in Los Angeles.