Whilst on holiday in Paris in 1960, Mori had fateful fitting with the infamous Coco Chanel. She claimed this meeting changed her life and she challenged herself to realise her own dream of designing haute couture. She returned to her small Tokyo office, where she had be designing significant numbers of costumes for directors including Ozu, Oshima and Kurosawa. She had been thinking of throwing in the towel but this meeting gave her new enthusiasm and a new challenge. By 1965 she had launched her won collection and had orders from prestigious stores such as Neiman Marcus.

In 1975 Mori moved to France and showed her collection in Paris, where she soon opened her atelier in 1977. She has since been commuting between Paris and Tokyo.

Mori is the Queen of couture in Japan, she has the patronage of Princess Masako, who favours her refined suits and floral evening gowns for formal functions. Her trademark east-meets-west blend of Mao collars, kimono sleeves and Western couture techniques have graced the likes of both Nancy Reagan and Hillary Clinton, Princess Grace of Monaco and Sophie Marceau.

In Paris in July 2004, Hanae Mori said goodbye to the fashion world, with her last Haute Couture collection. Her gowns were exquisitely embroidered with her trademark butterflies and her granddaughter 21 year old Izumi Mori wore her finale wedding gown. The audience rose to their feet for a last ovation.