Zapp was born in Riga, Governorate of Livonia (now Latvia) to a Baltic German mother and a British father.

[1] In 1932, while living in Estonia, he began developing the then subminiature camera by first creating wooden models, which led to the first prototype in 1936.

[1] The innovative design and technical solutions of Zapp's camera were patented around the world.

[3] In the 1960s, Zapp was named as the inventor in several patents granted to Minox GmbH for improvements and modifications of a subminiature camera.

In 2001, Walter Zapp received an honorary doctorate of the Latvian Academy of Sciences and was decorated with the Order of the Cross of Terra Mariana for his special services to the Republic of Estonia.