She made her film debut at the age of 17 in the motion picture "Heavenly Creatures" by Peter Jackson, and immediately made an impression. Her first Oscar nomination was for Ang Lee’s "Sense and Sensibility," but it was her interpretation of Rose in "Titanic" that revealed her to the international public and resulted in her second Oscar nomination. She was then nominated for her roles in "Iris", "Eternal Sunshine of the Spotless Mind" and "Little Children", and achieved recognition by winning the Oscar for Best Actress for her performance as an ex-Nazi in "The Reader" in 2009. Her other achievements back then included memorable and award-winning movies, among them "Revolutionary Road" directed by Sam Mendes and in which she again plays alongside Leonardo DiCaprio, “Finding Neverland” and "Romance & Cigarettes".

In 2010, Kate played the leading role in the HBO dramatic mini-series “Mildred Pierce”, in which she reinterpreted, over five hours, the role once played by Joan Crawford in the film of the same name. This performance won her three awards as Best Actress in a mini-series or television film: An Emmy Award in 2011, and a Screen Actors Guild Award and Golden Globe in 2012. To complete this long list of achievements, Kate was also awarded an Honorary César in 2012. In addition, she won the 2016 Golden Globe and BAFTA Award (British Academy of Film Awards) for Best Actress in a Supporting Role for the Danny Boyle motion picture “Steve Jobs”. This role also earned her a seventh Oscar nomination.