Porter was educated at the Lycée Français in Damascus, Fernhill Manor, then for a short time studying French and Old English at Royal Holloway College, London, before being expelled.
Her customers, some of whom also became her friends, included Baby Jane Holzer, Lauren Bacall, Talitha Getty, Bianca Jagger, Mick Jagger, Inaara Aga Khan, Jutta Laing (the wife of R D Laing), Pamela, Lady Harlech, Veronique Peck, Princess Margaret, Edna O'Brien, Sharon Tate, Elizabeth Taylor, and Pete Townshend.
[1][3] In 1971, Porter opened a store in New York financed by Michael Butler, the producer of the hit Broadway musical Hair.
It closed after six months, but she continued to sell very successfully at high-end boutiques across the United States; Giorgio Beverly Hills sold approximately $300,000 worth of Thea Porter designs per year in the mid-1970s.
Thea Porter Decorations Ltd went into receivership in February 1981; she subsequently worked from ateliers on Avery Row and Beauchamp Place.