Born in Valletta in 1932, Portelli studied at St Joseph High School, Rabat and at St Catherine
High School, Sliema.
Portelli started broadcasting at a tender age in radioplays with Rediffusion. In 1957 she joined the Radju Musketti cr1 with Charles Clews and Johnny Catania. In the sixties, together with her husband Paul, they formed ‘The Bluebirds’ to produce and present a children’s programme. In 1976 she was one of the protagonists in the radio-serial F’Bahar Wiehed, while in 1980 she presented a series of comedy programmes Fuq Tlieta Toqghod il-Borma.
Portelli has participated in several television drama productions in Maltese. She has also written many works for the theatre, radio, television, and night clubs. A regular contributor to the Maltese-Australian paper The Maltese Herald, she has visited Australia in 1982, in 1984, and in 1988 where she travelled from Adelaide to Mackay in Queensland as guest of the Maltese migrants’ committees. She has recorded two cassettes with Maltese songs and sketches. In her 1984 visit to Australia as the guest of the Maltese Australian Cultural Group of NSW, Portelli produced a musical comedy imhabba fil-Buskett which was a great success.
In 2000 Portelli was awarded the Midaija ghall-Qadi tar-Repubblika (MQR).
Gemma Portelli married Paul (d. 2001) and has a son, Martin, and a daughter, Kora.