Zapp was born in Riga, Latvia. In 1934, living in Estonia, he began developing the then subminiature camera by first creating wooden models, which led to the first prototype in 1936. It was introduced to the market in 1938. Minox cameras were made in VEF (Valsts Elektrofabrika). VEF made 17,000 Minox cameras. Every Minox lens was hand made from a small glass cube by young women, who had recently graduated from college and were looking for a job. Before the Russian occupation in 1940, Walter Zapp moved to Germany. After World War II, in 1945, he founded the Minox GmbH in Wetzlar. The company still exists.
In 2001, when he went to Latvia for the last time, he said that he had gone to celebrate his 100th birthday in Latvia. He died at age of 98, in Binningen near Basel, Switzerland.
Spycamera The MINOX Story, Morris Moses & John Wade, Hove Collectors Books, ISBN 1-874707-28-6