Actress Kelley Mack, recognized for her portrayal of Addy in the ninth season of “The Walking Dead,” passed away on Saturday, August 2, 2025, at the age of 33 due to glioma of the central nervous system. The Cincinnati, Ohio, native died peacefully in her hometown, attended by her mother Kristen and aunt Karen.
Known at birth as Kelley Lynne Klebenow, Mack disclosed her cancer diagnosis in January via an Instagram post. She revealed that she was diagnosed with diffuse midline glioma, a rare variant of astrocytoma cancer. Mack detailed how her symptoms initially manifested as persistent lower back pain, which she initially attributed to a slipped disc.
As the pain intensified, Mack encountered neuropathic itching in her right quadricep, followed by sharp pains in her legs and back. Her symptoms became so severe that she resorted to sleeping in a recliner for an entire month, as lying down was too painful. On the eve of Thanksgiving, emergency MRIs at a hospital identified an abnormal mass in her spinal cord.
The National Cancer Institute states that diffuse midline gliomas are tumors of the central nervous system that originate in the brain or spinal cord. Treatment options include surgery, radiation therapy, and chemotherapy. Currently, approximately 3,940 individuals in the United States are living with diffuse midline gliomas, with a relative five-year survival rate of 42.2 percent, according to the institute.
Following a biopsy surgery on her spinal cord, Mack lost mobility in her right leg and most of her left leg, necessitating the use of a walker and wheelchair. She underwent radiation therapy in Cincinnati, where her family resides. In March, she posted a video on Instagram displaying her ability to walk up stairs, marking significant progress in her condition.
Mack’s sister Kathryn announced her passing on Instagram on Tuesday, stating that her sister “passed peacefully on Saturday evening” and described her as courageous, particularly in her decision to reunite with God. The family’s statement noted Mack has already visited loved ones as various butterflies.
In addition to “The Walking Dead,” Mack appeared in season eight of “Chicago Med” as Penelope Jacobs and featured in a 2019 episode of “9-1-1.” Her film credits include roles in “Mr. Manhattan” and “Delicate Arch” in 2024, as well as the forthcoming 2025 film “Universal,” which she had been promoting on social media recently.
The actress also had a substantial career in commercial acting and voice-over work, appearing in advertisements for Dr. Pepper, Ross Stores, Dairy Queen, and Chick-fil-A. Throughout her career, she held 35 acting credits and five producing credits, and collaborated as a screenwriter on projects with her mother, including “On The Black,” a college baseball story set in the 1950s loosely based on her maternal grandparents who attended Ohio University.
Mack’s interest in storytelling began early when she received a mini video camera as a birthday gift. She initiated her career as a child actress in commercials and later earned an acting award from the Tisch School of the Arts for her role in “The Elephant Garden,” which received the Student Visionary Award at the 2008 Tribeca Film Festival.
She completed her education at Hinsdale Central High School in 2010 and obtained a bachelor’s degree in cinematography from Chapman University’s Dodge College of Film in 2014. She had been living and working in Los Angeles for the past decade.
Peers and friends have offered condolences, recalling Mack as a talented individual. Alanna Masterson, a fellow “The Walking Dead” actress, expressed pride in having shared their final episode together. The family described Mack as known for her warmth, creativity, and steadfast support for those around her, with her enthusiasm and commitment inspiring many in the industry.
A celebration of life ceremony is scheduled for August 16 in Glendale, Ohio, with another event planned for Los Angeles at a date yet to be determined. Mack is survived by her parents, Kristen and Lindsay Klebenow; sister Kathryn; brother Parker; grandparents Lois and Larry Klebenow; and boyfriend Logan Lanier.
