Miedinger was educated at the Zürich Kunstgewerbe schule 1928–32 and then at the Académie Ranson in Paris. He worked in Zürich with Orell Füssli and an advertising agency, before he opened his own studio there. He created logotypes, posters, packaging, corporate identities and exhibitions for industry and government. In 1945 he was commissioned to work on a social programme for the charity Winterhilfe. Miedinger also contributed to the Swiss entries for the Brussels Expo 1958 and Montreal Expo 1967. For 25 years he designed window displays for Credit Suisse, Zürich. In 1968–72 he was a member of the jury for the best Swiss posters of the year. In the same period he was president of the Verband Schweizer Graphiker (later ASG).