"The Home Alone" icon, who was also known for her iconic performance in Schitt’s Creek, died on January 30.
Aged 71 years old, Catherine died at her home in Los Angeles following a brief illness.
The Los Angeles County Medical Examiner’s Office has confirmed the actress’ immediate cause of death was pulmonary embolism, with rectal cancer an underlying cause.
The news was first published in TMZ, who note her death certificate said she was cremated and her remains were returned to her husband Robert “Bo” Welch.
Catherine had dual Canadian and American citizenship, and was best known for her sharp comic timing and expressive characters.
She had a long-running collaboration with fellow comedic star Eugene Levy as the heads of the Rose family in "Schitt’s Creek".

Catherine O'Hara as Moira Rose in "Schitt's Creek".
Prior to being the matriarch in "Schitt’s Creek", O’Hara filled the role of Kate McCallister in "Home Alone" and "Home Alone 2". She also played a maternal role as Delia Deetz in "Beetlejuice" in 1988.
The Hollywood actress won an Emmy Award in 2020 for her role as the over-the-top Moira Rose. This year, she was nominated for a Golden Globe for her role in The Studio, but was notably absent from the ceremony.
Another of O’Hara’s most recent roles was in the second season of Prime Video’s "The Last of Us", where she starred alongside Pedro Pascal, who was among those who paid tribute.
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Sharing a picture of the pair on set, Pedro wrote: "Oh, genius to be near you. Eternally grateful. There is less light in my world, this lucky world that had you, will keep you, always, Always.
"The one and ONLY #CatherineOHara."
Another emotional tribute came from Macauley Culkin, who played her on-screen son Kevin in the "Home Alone" franchise.
"Mama. I thought we had time,’ he wrote alongside photos of the duo, ‘I wanted more. I wanted to sit in a chair next to you. I heard you. But I had so much more to say."
* This article was originally published on Extra.ie.
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