She said on Instagram alongside the snaps of her mum: “After my own breast cancer diagnosis in 2023, I urged my mother and sister to take the Breast Cancer Lifetime Risk Assessment test.
“My mother scored 26.2%.
“Her yearly mammogram had just come out clear but because of that high score I insisted she get an MRI. Shortly after that MRI, my mother was diagnosed with Stage 1 HER2 breast cancer.”
According to Munn, Kim has since completed 12 rounds of chemotherapy and will continue receiving Herceptin infusions – a targeted therapy drug – through the autumn.
The Newsroom star also revealed the emotional toll of seeing her mother go through the illness.
“From my mom being there after my double mastectomy to me being there after hers,” she said.
Munn added: “From me having to find an oncologist, to my mom and I sharing one. I can tell you this: going through cancer is really hard.
“But there’s something about watching a loved one go through it that is even more heartbreaking.”
Munn said she had spent “many nights” caring for Kim when the effects of chemotherapy became overwhelming.
“It’s no small feat to realise you can’t do it for them,” she said – adding: “To anyone out there who is taking care of someone or has made it their profession to do so, thank you. These fights can feel near impossible without you.”
In her post, Munn included photos of herself and Kim at a medical appointment, with a video of Kim cooking after surgery, a visit from Munn’s husband, John Mulaney, 42, and a throwback image of the two women.
The New Girl actor also paid tribute to Kim’s spirit and resilience during her treatment.
“I want to say how proud I am of my mom,” Munn wrote.
She added: “She’s handled all of this with bravery and humour while still driving us crazy (just days after her double mastectomy she tried to do laundry and make dinner – she’s insane.)”
Olivia concluded by sharing resources for early detection, encouraging followers to take the free Tyrer-Cuzick Risk Assessment and to request breast MRIs when appropriate.
She added: “My mom wanted me to tell you that she hopes by sharing her story it will help save someone’s life.”
Munn previously kept her diagnosis private, only revealing it in March 2024.
“I went from feeling completely fine one day, to waking up in a hospital bed after a 10-hour surgery the next,” she said at the time.
She also thanked John for his support, saying: “Being there before I went into each surgery and when I woke up, always placing framed photos of our little boy Malcolm so it would be the first thing I saw.”
