In 1955 she made her stage debut at the age of nine, and her television debut in ‘Dixon of Dock Green’ at the age of 12 while her film debut came in 1963 with ‘Wings Of Mystery.’ Other Sixties television appearances included: ‘ITV Play Of the Week’, ‘The Wednesday Play’, ‘Cluff’, ‘The Newcomers’, ‘Danger Man’, ‘Mrs Thursday’, ‘Mr Rose’, ‘Man In A Suitcase’, ‘ITV Playhouse’ and ‘Happy Ever After’. It was her role as Maria Copper in ‘The Newcomers’ which first brought her to a wider audience when she appeared in the show for two years between 1965 – 1967 as the teenage daughter to a family who move from London to the countryside. Her films in the Sixties were: ‘Here We Go Round The Mulberry Bush’, ‘To Sir With Love’ and ‘Berserk’ in 1967; ‘Prudence & The Pill’ and ‘Hammerhead’ in 1968 and ‘Three Into Two Won’t Go’ and ‘Two Gentlemen Sharing’ in 1969. ‘Mulberry’ is based on a coming-of-age book by Hunter Davies, who went on to become a Sunday Times columnist and the Beatles' official biographer and Judy’s character is Mary Gloucester, the main romantic interest. She then went on to the internationally successful ‘To Sir With Love’, which starred Sidney Poitier. Judy featured as a schoolgirl who develops a crush on the new teacher. Incidentally, Judy took part in a promotional tour in the U.S. for ‘To Sir With Love’ and was credited for bringing the mini-skirt to America. She was 18 when she was featured as the young wayward girl Pamela Date in the film. When discussing the movie, she commented, “When you act a scene with Sidney Poitier he listens intently to every word you say. You can feel your words hit him. He makes the scene utterly real.

‘Berserk’ featured Joan Crawford, Ty Hardin, Diana Dors and Judy as Angela Rivers, in a horror movie set in a travelling circus. Deborah Kerr and David Niven starred in ‘Prudence & The Pill’, with Judy as Geraldine Hardcastle in a tale in which Prudence Hardcastle’s birth prevention pills have been replaced with aspirin and there is a search to find the culprit. She starred as Jane Archer in ‘Two Gentlemen Sharing’, her final feature of the 1960s. In 1968 she was placed second in the Laurel Awards as Best Female New Face. Judy appeared in more than 35 movies incuding ’10 Rillington Place’, ‘Carry On England’, ‘Doomwatch’, ‘Brannigan’, ‘The Eagle Has Landed’ and ‘Fear in the Night.’ She also featured in more than two dozen TV series which included ‘Danger Man’, ‘Space 1999’. Danger UXB’ and ‘Poldark’. ‘Star Maidens’ was a German sci-fi series and when Judy decamped to America in October 1984 she appeared in series such as, ‘Murder She Wrote’, ‘The A-Team’, ‘Hotel’, ‘McGyver’, ‘Mad About You’, ‘Star Trek Voyager’, ‘Touched By An Angel’, ‘Charmed’ and ‘Gilmore Girls.’ ‘Inseminoid’ was a low-budget movie in which she starred as Sandy, a member of an expedition who are excavating on a distant planet. An alien monster rapes her and she gains superhuman strength and gives birth to two mutant babies. A documentary short ‘Judy Geeson: Inseminoid Girl’ was released in 2004.

Following her trip to America, she decided to settle there for a while and met actor Kristoffer Tabori, whom she married in 1985, and the two settled in California. When they eventually split up in 1989, Judy opted to remain in L.A. where she was to join Ian McKellan, Jenny Agutter, Olivia Hussey and other British actors at a school in Watts, where they taught Shakespeare to youngsters.
Judy opened her own antique shop ‘Blanche' in Los Angeles in 1999. The shop name changed to ‘Blanche & Co,’ but closed in 2009.