She came to Athens with her family in 1922. During 1930-1933, she studied pottery at the Vienna Arts and Crafts School with Michael Powolny and Robert Obsieger. Returning to Athens in 1933, she visited regions in which ancient Greek potters worked, collecting a great number of different clay types. In 1945, she went to Paris and worked with Marcel Gimond. During 1947-1949 she lived in Argentina, where she studied the Inca and Indio art and culture. In June 1949, she returned to Greece; during 1953-1967 she travelled once again to the Americas as well as Egypt, Japan, India, Thailand, Bali, China, Cambodia, Java, Iraq, Nepal and Persia. In 1974, the Academy of Athens honoured her for her work and in 1980 she became the first woman nominated as an Academy member.
Her work has been shown in solo exhibitions in Greece and around the world. She also participated in group and international events, including Panhellenic exhibitions, the 1955 International Ceramics Fair in Cannes, the international contemporary sculpture exhibitions held in the Musee Rodin in 1956 and 1961, the 1965 International Sculpture Panathenaia exhibition in Athens and the New York World Fair of the same year, the Paris Salons de la Jeune Sculpture in 1968 and 1969, as well as the 1959 Sao Paulo Biennale, where she won first prize, and the 1965 Alexandria Biennale.
Until around the mid-1950’s, Frosso Efthymiadi worked exclusively with clay, creating busts and full figures, vases and figurines, but above all a substantial number of animals; indeed, she is considered as the first sculptor to pursue animal sculpture in Greece. In 1955, she turned to metal, abandoning at the same time her realistic output and adopting a freer style. Using electric or oxyacetylene welding to join bronze or iron plates or rods which she forged herself, and working within the same thematic field she created abstract compositions, either static or in motion, in which the void plays a prominent role.