Hans Erni studied in Lucerne and Paris. He later married his colleague Gertrude Bohnert (died 1948 after a riding accident) and was known for his mosaics and graphics, which were often characterized by geometric lines. His daughter Simone also became a recognized artist. In his youth he was an avid sportsman (hockey, ski jumping and cross country).
However, Erni worked as a painter, sculptor, graphic artist and ceramist. He created about 90 stamp issues for the Swiss post office, the United Nations, and for Liechtenstein, and illustrated about 200 non-fiction books, encyclopedias and literary works. Because he was a follower of Marxism, he had problems in the 1950s with being accepted in Switzerland. Later, however, he became one of the most popular Swiss artists. In his home town of Lucerne, he was accorded his own museum.