After her studies, from 1946 to 1947, she worked as an editor at the architecture magazine Costruzioni. In 1949, Ferrieri joined her husband, Giulio Castelli, in founding the furniture company
Kartell, which would become a leading company in the manufacture of high-quality plastic furniture, lighting, and homewares. Plastic at this time was considered to be an industrial material and was not typically seen inside the home. According to historian Catharine Rossi, Ferrieri experienced problems in partnership due to her trouble in balancing her role as a wife and as an architect designer. She only agreed to work at Kartell, per her husband’s request, after two of his business partners left. Anna Ferrieri designed the first chair from a single mould in 1968. Anna Castelli Ferrieri laid the Kartell foundations on geometric shapes, bold color, and highly polished finishes. Today, even after 40 years of production the Componibili is still one of
Kartell's best selling furniture items. A more compiled list of all of Ferrieri’s exhibitions are listed below. Ferrieri worked as
art director for Kartell from 1976 to 1987, and is most known for her use of materials such as metal and
polyurethane. Through her use of plastics, a fairly unused furniture material at the time, she was able to create novel forms that were both elegant and functional. In addition to her work, she founded and was a member of several organizations including; The Movement of Architecture Studies (MAS) of Milan, 1945; National Institution of Urban Planning (NIU), 1952–1956 and later became president from 1969–1971; Italian Industrial Design Association (IDA) in 1956. She also published two books; one in 1984, “From Project to Product: Plastic and Design”, and the second book was published in 1991, “The Interface of Material”, which explains the responsible behavior on the part of designers. In addition, she also has published a profound list of articles. ==Style, technique, and artwork==