Werner Arnold Anek Hahn was the son of Paul Daniel Hahn*, professor of chemistry at the South African College in Cape Town, and his wife Marie Aneck Hahn, born Black. Werner studied at the South African College from 1893 to 1898, matriculating in 1895. In 1898 he passed the first mining examination of the University of the Cape of Good Hope. That same year he was appointed as an assistant in the college's Department of Chemistry, a position he held until he resigned at the end of 1901.
From 1897 to 1901 Hahn was in charge of the second order meteorological station at the South African College. A summary of his observations was published annually in the Report of the Meteorological Commission of the Cape of Good Hope for these years.
In 1909 Hahn accompanied T. Tonnesen* on an expedition to the Kaokoveld for the South West Africa Company. Hahn wrote a series of 18 Reports of the Kaokoveld Expediton (1909), which are housed in the National Archives of Namibia. The next year he presented a collection of rocks, including basalts and andesites of unknown age, from the northern parts of German South West Africa (now Namibia) to the South African Museum in Cape Town.
Hahn later made his living as a farmer in the Transvaal. On 28 October 1911 he married Marjorie Goldie Black, with whom he had three sons.