August 6, 2025 – The entertainment industry is reeling from the tragic loss of actress Kelley Mack, best known for her role as Addy in The Walking Dead, who passed away peacefully on August 2, 2025, in her hometown of Cincinnati, Ohio. She was 33 years old. Her death followed a courageous, nearly year-long battle with diffuse midline glioma (DMG), a rare and aggressive form of central nervous system glioma.
A Life Cut Short: Mack’s Diagnosis and Final Days
Mack first shared her devastating diagnosis publicly in January 2025, revealing she suffered from an extremely rare astrocytoma cancer typically seen in children. The tumor aggressively impacted her spinal cord and brain. Initial symptoms appeared in October 2024 as persistent lower back pain, escalating dramatically around Thanksgiving when an MRI revealed an “abnormal mass” on her spinal cord.
“Due to the biopsy surgery on my spinal cord, I lost the use of my right leg and most of my left leg, so I now get around with a walker and a wheelchair,” Mack wrote on Instagram. Despite grueling treatments, including proton radiation therapy, she maintained remarkable resilience. In March 2025, she documented herself “re-learning how to walk” during physical therapy, captioning a video: “Life has also had its ups and downs lately am I right?”
Mack spent her final months surrounded by family—her mother Kristen, aunt Karen, siblings Kathryn and Parker, and devoted boyfriend Logan Lanier. Her sister Kathryn’s heartbreaking Instagram announcement described Mack’s peaceful passing: “Such a bright, fervent light has transitioned… Kelley has already come to many loved ones in the form of butterflies.” She poignantly added, “As her sister, I want you all to know how brave that tough SOB was… I’m so f–king proud of her.”
A Radiant Career: From Child Actor to Beloved Performer
Born Kelley Lynne Klebenow on July 10, 1992, Mack’s passion for storytelling ignited after receiving a mini video camera as a child. She began acting in commercials for brands like Dr Pepper, Dairy Queen, and Budweiser, later studying cinematography at Chapman University. Her breakthrough came with the award-winning short film The Elephant Garden (2008), which won the Student Visionary Award at the Tribeca Film Festival.
Key Roles and Legacy:
- The Walking Dead (Season 9): Played Addy, a Hilltop Colony resident, appearing in five impactful episodes during the Whisperers storyline. She reflected: “I was only supposed to be in 2 episodes… I was grateful to work on five.”
- Chicago Med & 9-1-1: Portrayed Penelope Jacobs, showcasing her versatility in medical dramas.
- Spider-Man: Into the Spider-Verse: Served as the voice match for Gwen Stacy (Hailee Steinfeld), later reprising the role in a Hyundai commercial.
- Producer & Filmmaker: Produced horror short A Knock at the Door (2016) and wrote/directed Positive (2015). Her final project, the sci-fi film Universal, in which she starred and executive produced, premiered recently in Hollywood.
A Creative Family and Enduring Spirit
Mack hailed from a deeply artistic family. She co-wrote screenplays with her mother, Kristen, including On The Black—a baseball drama inspired by her grandparents. Her brother, Parker Mack, is an actor (Chasing Life, Faking It). Beyond film, she loved tennis, hiking, fantasy football, country music, and playing piano.
Memorial Services and Tributes
A public remembrance will be held on August 16 at the Glendale Lyceum in Glendale, Ohio. A second celebration of life is planned for Los Angeles, where Mack lived and worked for over a decade. Co-stars flooded social media with tributes:
- Alanna Masterson (The Walking Dead): “What an incredible human. So proud to have fought alongside her.”
- Michael E. Satrazemis (Director): “A bright light on every level… All my love to those who loved her.”
Understanding Glioma: The Disease That Took Kelley
Mack’s cancer, diffuse midline glioma (DMG), is a brutal tumor arising from glial cells in the brain or spinal cord. According to the Mayo Clinic, it’s exceptionally rare in adults, with limited treatment options and a poor prognosis. Her public documentation of her fight raised critical awareness about this devastating illness.