She fought a long battle with cancer before passing away at a hospital near her Sussex home on Thursday.
Born in France, Walker made a name for herself in Britain as one of the country's leading couture designers.
She provided Diana with many of her most iconic outfits, having first worked with her three months after her wedding to Prince Charles in 1981. The Princess was buried in a black dress designed by Walker that she had bought in the weeks leading up to her death.
In a statement, her family said: ''Catherine Walker overcame young widowhood and fought cancer twice with enduring bravery.
''She built one of the most successful British couture brands and at the same time raised a loving family. Catherine Walker has dressed many of the world's most beautiful women.''
Walker studied philosophy at the Universities of Lille and Aix-en Province, then moved to London after meeting solicitor John Walker.
He died suddenly in an accident in 1975, leaving Walker to raise their two young daughters alone.
She started studying fashion at night school the following year, selling clothes from a basket on Kings Road in Chelsea during the day, and then set up her own business.
Walker, who also designed a wedding dress for Lady Helen Taylor, was unusual for staying out of the limelight during her career, choosing not to show her collections on the runway.
Her designs spoke for themselves however, with Walker named Designer of the Year for Couture at the British Fashion Awards in 1990 and Designer of the Year for Glamour the following year.
Her family said she suffered failing health in recent years, but despite that, hand-picked and trained a design team under the brand name Catherine Walker & Co.
They said: ''With this team, she developed a portfolio of designs through to 2012 to carry forward her philosophy and the unique handwriting of her brand into the 21st century.
''She will be missed by both this team and her family, all of whom are determined to grow the brand and the legacy of this great designer.''
Walker had suffered from breast cancer and was a founding sponsor of charity Breast Cancer Haven.
Details of a memorial service will be announced at a later date, but it is expected to take place in a month's time. A private family funeral service has been arranged.