After studying at the École des Beaux-Arts in Paris, Kennedy started her career in the 1960s at the London design firm of David Mlinaric, whose clients included Mick Jagger and Eric Clapton. In 1968, after spending three years working as partner with Mlinaric, she won a competition to design the Grosvenor House Hotel, launching her own company with Michael Sumner that same year. In 1986, she reformed as Tessa Kennedy Design, Ltd., a company which has won several design accolades. Her clients have included De Beers, Stanley Kubrick, George Harrison, King Hussein of Jordan and London hotels Claridge’s, The Berkeley, and The Ritz for which she was voted Designer of the Year.