Kelley Mack, best known for her role as Addy in AMC's "The Walking Dead," has died at the age of 33 after a battle with a rare and aggressive brain cancer. Mack, born Kelley Lynne Klebenow in Cincinnati, Ohio, passed away peacefully on August 2, 2025, in her hometown, surrounded by her mother Kristen and aunt Karen.
Mack publicly shared her diagnosis of central nervous system glioma in September 2024. This rare cancer arises in the brain or spinal cord and is known for its rapid progression and difficult treatment. According to the Cleveland Clinic, gliomas form when glial cells, which support nerves and help the central nervous system, grow uncontrollably. These tumors tend to grow in the brain but can also form in the spinal cord. Mack underwent aggressive treatment in hopes of beating the disease. In January 2025, she shared that the biopsy surgery on her spinal cord caused her to lose the use of her right leg and most of her left leg, requiring her to use a walker and wheelchair. Despite these hardships, Mack remained positive, sharing videos of her rehabilitation progress and smiling at her illnesses. In March 2025, she posted a video of herself walking up and down stairs with the help of her boyfriend, Logan, marking it as a significant achievement.
Mack began her acting career with commercials and advertisements. Her early success led to her debut in the 2008 film "The Elephant Garden," for which she received the Acting Award from the Tisch School of the Arts and the Student Visionary Award at the Tribeca Film Festival. Before her role in "The Walking Dead," Mack appeared in several shorts and TV miniseries, including "Unusual Suspects" (2015), "Grayson: Earth One" (2015), "Not Your Average Joe" (2016), and "Unscrewed" (2016). She amassed dozens of TV and film credits throughout her career. She was cast as Penelope Jacobs in Season 8 of "Chicago Med" and appeared on FOX's "9-1-1". Mack also had roles in movies like "Alice" in "Broadcast Signal Intrusion" and "Wilda" in the recently released "Delicate Arch". Additionally, she voiced Gwen Stacy in the animated film "Spider-Man: Into the Spider-Verse".
Mack's most significant role came as Addy in Season 9 of "The Walking Dead". She appeared in five episodes as a resident of the Hilltop Colony. Her portrayal of Addy, a stoic yet gentle character, quickly gained recognition.
Her family described her as “a bright, fervent light” and a soul who continues to visit loved ones, “in the form of various butterflies”. Her sister, Kathryn Klebenow, shared a statement on Mack's Instagram, saying, "Such a bright, fervent light has transitioned to the beyond, where we all eventually must go. Kelley passed peacefully on Saturday evening with her loving mother Kristen and steadfast aunt Karen present. Kelley has already come to many of her loved ones in the form of various butterflies".
A recognition and remembrance of Kelley's life will be held in Glendale, Ohio, on August 16, with a celebration of life planned in Los Angeles at a future date. Mack is survived by her parents, brother Parker, sister Kathryn, and grandparents.
