Actress Kelley Mack, known for her role as Addy in season nine of “The Walking Dead,” died Saturday, August 2, at age 33 after battling glioma of the central nervous system. The Cincinnati native passed away peacefully in her hometown, surrounded by her mother Kristen and aunt Karen.
Born Kelley Lynne Klebenow, Mack announced her cancer diagnosis in January through an Instagram post. She shared that she had been diagnosed with diffuse midline glioma, noting that it is a particularly rare form of astrocytoma cancer. The actress explained that her symptoms began with persistent lower back pain, which she initially thought was a slipped disc.
The pain progressively worsened, with Mack experiencing neuropathic itching in her right quadricep, followed by shooting pains in her legs and back. Her symptoms grew so intense that she had to sleep in a recliner for an entire month, as lying down caused her too much pain. On Thanksgiving Eve, emergency MRIs at a hospital revealed an abnormal mass in her spinal cord.
According to the National Cancer Institute, diffuse midline gliomas are central nervous system tumors that begin in the brain or spinal cord. They are treated through surgery, radiation therapy, and chemotherapy. According to the institute, around 3,940 people in the United States are currently living with diffuse midline gliomas, and the relative five-year survival rate is 42.2 percent.
Due to biopsy surgery on her spinal cord, Mack lost the use of her right leg and most of her left leg, requiring her to use a walker and wheelchair for mobility. She received radiation treatment in Cincinnati, where her family lives. In March, she shared a video on Instagram showing herself walking up stairs, noting it was significant progress for her condition.
Mack’s sister Kathryn announced the death on Instagram Tuesday, writing that her sister “passed peacefully on Saturday evening” and describing her as brave, especially when she decided to be reunited with God. The family statement indicated that Mack has already visited loved ones in the form of various butterflies.
Beyond “The Walking Dead,” Mack appeared in season eight of “Chicago Med” as Penelope Jacobs and in an episode of “9-1-1” in 2019. Her film work included roles in “Mr. Manhattan” and “Delicate Arch” in 2024, as well as the upcoming 2025 film “Universal,” which she had been promoting on social media in recent months.
The actress also worked extensively in commercial acting and voice-over work, appearing in advertisements for Dr. Pepper, Ross stores, Dairy Queen and Chick-fil-A. She held 35 actress credits and five producer credits during her career and worked as a screenwriter on projects with her mother, including “On The Black,” a 1950s era college baseball story loosely based on her maternal grandparents who attended Ohio University.
Mack’s passion for storytelling developed at a young age when she received a mini video camera as a birthday gift. She began her career as a child actress in commercials and later received an acting award from the Tisch School of the Arts for her first role in “The Elephant Garden,” which was honored with the Student Visionary Award at the 2008 Tribeca Film Festival.
She completed her studies at Hinsdale Central High School in 2010 and went on to receive a bachelor’s degree in cinematography from Chapman University’s Dodge College of Film in 2014. For the past ten years, she had lived and worked in Los Angeles.
Colleagues and friends have shared condolences, remembering Mack as a talented and sweet soul. Alanna Masterson, who also starred in “The Walking Dead,” expressed pride in having fought alongside her in their final episode together. The family described Mack as known for her warmth, creativity, and unwavering support for those around her, with her infectious enthusiasm and dedication inspiring countless others in the industry.
A celebration of life ceremony is scheduled for August 16 in Glendale, Ohio, with another celebration planned for Los Angeles at a date 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.
