The daughter of musician and composer Dot Mendoza and her first husband, Frederick John Morton, June Mendoza, toured with her mother as a small child, working in small mime parts and crowd scenes for the opera, ballet, musicals and revue. From age 12 her interest in acting took second place, as she began focusing more intently on art. She took life drawing at fourteen and from age seventeen was working professionally as an artists. Her early work included illustrating book jackets, magazine illustrations, town-planning exhibition artwork, record sleeves, some portraits and the adventure comic strip Devil Doone.
In the late-1940s Mendoza contributed illustrations for two books, one of these being The Tail is Familiar (1948), a collaboration with her mother. By then she already won Ealing Studio's 1946 Overlanders art competition with her portrait of actor Chips Rafferty. To celebrate the award Woman magazine used the painting as the cover for one of its issues ('Chips Rafferty as Cover Boy' SunSun] 11 October 1946, p.9). Interesting, competition had been open to both professional and amateur artists and attracted more than 2,000 entries.
Prior to immigrated to England in the late-1940s, Mendoza continued to focus her career towards art, while also occasionally working as an actress - both on stage and on radio. In 1947, for example, she starred as Ruth in the Macquarie Radio Theatre feature Dear Ruth. Broadcast on 21 December the producer was Lawrence H. Cecil. Earlier that same year she had appeared in the Minerva Theatre production of The Wind of Heaven. She also went through to the final 15 entrants in the King's Cross section of the Miss Australia beauty contest. In its report on the competition the Sun newspaper records that the '22 year old brunette from Elizabeth Bay' was already 'an experienced actress, having played in leading theatres in Sydney and Melbourne' ('Cross Girls are Keen.' Sun 8 September 1947, p.7).
Such was the interest in Mendoza career following her move to Britain, Dick Bentley interviewed her from London in March 1950. It was broadcast around Australia on relay. During her early English career she worked for Hulton Press producing illustrations and comics for Eagle's companion title Girl. After five years she transitioned into full time portraiture with subjects including Prince Philip, Duke of Edinburgh, Sammy Davis Junior, Sean Connery, Princess Diana, Queen Elizabeth II (twice), HM Queen Elizabeth The Queen Mother, Sir William McMahon, Prince Edward, Baroness Margaret Thatcher, Sir John Major, and Sir John Gorton. The latter work, became the official Parliamentary portrait following its acquisition in 1972. It is the first and only official portrait of a Prime Minister by a woman artist.
Mendoza's career in England also included occasional stints on the stage, including a role in the West End production of Me and My Girl (with Lupino Lane).
